Why would Voldemort put a boat in the Horcrux cave lake if he can fly?

Question

From the novel, Harry Potter and the Half-Blood Prince:

Immediately a thick coppery green chain appeared out of thin air, extending from the depths of the water into Dumbledore’s clenched hand. Dumbledore tapped the chain, which began to slide through his fist like a snake, coiling itself on the ground with a clinking sound that echoed noisily off the rocky walls, pulling something from the depths of the black water. Harry gasped as the ghostly prow of a tiny boat broke the surface, glowing as green as the chain, and floated, with barely a ripple, toward the place on the bank where Harry and Dumbledore stood.

“How did you know that was there?” Harry asked in astonishment.

“Magic always leaves traces,” said Dumbledore, as the boat hit the bank with a gentle bump, “sometimes very distinctive traces. I taught Tom Riddle. I know his style.”

“Is…is this boat safe?”

“Oh yes, I think so. Voldemort needed to create a means to cross the lake without attracting the wrath of those creatures he had placed within it in case he ever wanted to visit or remove his Horcrux.”

“So the things in the water won’t do anything to us if we cross in Voldemort’s boat?”

“I think we must resign ourselves to the fact that they will, at some point, realize we are not Lord Voldemort. Thus far, however, we have done well. They have allowed us to raise the boat.”

Why would Voldemort need a boat if he can fly?

Did he not know how to fly yet when he put the locket inside the cave?

Answer 1

The boat limits the chance of crossings.

The requirement of using the boat is meant to keep most wizards from being able to cross, while Voldemort himself would be able to cross just as easily in the boat as he would by flight. He crossed back from the lake quite easily when he used Kreacher to test the defenses of the cave.

“And then the Dark Lord sailed away, leaving Kreacher on the island …’

Harry could see it happening. He watched Voldemort’s white, snake-like face vanishing into darkness, those red eyes fixed pitilessly on the thrashing elf whose death would occur within minutes, whenever he succumbed to the desperate thirst that the burning potion caused its victim … but here, Harry’s imagination could go no further, for he could not see how Kreacher had escaped.

‘Kreacher needed water, he crawled to the island’s edge and he drank from the black lake … and hands, dead hands, came out of the water and dragged Kreacher under the surface …”
_{^{- Harry Potter and the Deathly Hallows, Chapter 10 (Kreacher’s Tale)}}

If flight was a possible method of crossing the lake, it would be more difficult to limit who could cross the lake. Making the boat the only possible way to cross limits other wizards’ capability to cross it. First of all, the boat is hidden in a way that few wizards would be capable of finding it.

“But why have they let us?’ asked Harry, who could not shake off the vision of tentacles rising out of the dark water the moment they were out of sight of the bank.

‘Voldemort would have been reasonably confident that none but a very great wizard would have been able to find the boat,’ said Dumbledore. ‘I think he would have been prepared to risk what was, to his mind, the most unlikely possibility that somebody else would find it, knowing that he had set other obstacles ahead that only he would be able to penetrate. We shall see whether he is right.”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 26 (The Cave)}}

He also limited the boat to only be capable of carrying one qualified adult wizard.

“Dumbledore chuckled. ‘Voldemort will not have cared about the weight, but about the amount of magical power that crossed his lake. I rather think an enchantment will have been placed upon this boat so that only one wizard at a time will be able to sail in it.”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 26 (The Cave)}}

Therefore, having the only possible way to cross the lake be the boat ensured certain limitations on who could cross without affecting Voldemort’s ability to cross the lake himself.

At that time, he may have not yet learned.

It is in no way certain that Voldemort knew how to fly when he hid the locket in the cave. Several years separate Voldemort’s creation of the locket Horcrux and the first known instance of his flying unaided. He acquired the locket as a young man.

“But before they were sure beyond doubt that the cup and the locket were both gone, the assistant who had worked at Borgin and Burkes, the young man who had visited Hepzibah so regularly and charmed her so well, had resigned his post and vanished. His superiors had no idea where he had gone; they were as surprised as anyone at his disappearance. And that was the last that was seen or heard of Tom Riddle for a very long time.”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 20 (Lord Voldemort’s Request)}}

At the time he would have turned the locket into a Horcrux, he was still near the beginning of his path into further magical knowledge. For ten years after that, he disappeared from public view entirely, and used this time to further his knowledge.

“Ten years separate Hokey’s memory and this one, ten years during which we can only guess at what Lord Voldemort was doing …”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 20 (Lord Voldemort’s Request)}}

He tells Dumbledore he has accomplished much since leaving Hogwarts, though he does not give details.

“I have come to you to ask that you permit me to return to this castle, to teach. I think you must know that I have seen and done much since I left this place. I could show and tell your students things they can gain from no other wizard.”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 20 (Lord Voldemort’s Request)}}

During that time, he had experimented and tested the boundaries of magic. He may have continued to do similar experimentation with magic later into his life as well.

“Certainly,’ said Voldemort, and his eyes seemed to burn red. ‘I have experimented; I have pushed the boundaries of magic further, perhaps, than they have ever been pushed –”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 20 (Lord Voldemort’s Request)}}

It is not known when exactly Voldemort gained the ability to fly unaided. At the time Quidditch Through the Ages was written, no method of flying unaided in human form was known. Presumably, this means that the wizarding public had not seen Voldemort take flight at the time Quidditch Through the Ages was written.

“No spell yet devised enables wizards to fly unaided in human form. Those few Animagi who transform into winged creatures may enjoy flight, but they are a rarity.”
_{^{- Quidditch Through the Ages}}

As it references a Quidditch game that was played in 1994, Quidditch Through the Ages was therefore published either in or after 1994. That means it had been published after Voldemort’s first rise to, then fall from, power.

“The exception to this general rule is Japan, where Quidditch has been gaining steadily in popularity over the last century. The most successful Japanese team, the Toyohashi Tengu, narrowly missed a win over Lithuania’s Gorodok Gargoyles in 1994.”
_{^{*- Quidditch Through the Ages}}

This does not necessarily mean that Voldemort only gained the ability to fly unaided after 1994, but it would mean that he was not flying publicly before then. Additionally, since he had not been out of Hogwarts for long when he created that Horcrux, and he spent many years after that increasing his knowledge and skill in magic, it should not be presumed that he already had the ability to fly unaided when he turned the locket into a Horcrux.

Answer 2

Because a boat was not obvious. Why put the Horcrux on an island if any competent witch or wizard could just fly over on a broom? There must, therefore, be a curse on flying within the cavern, as A bakker suggested in the comments. A boat can be hidden, both magically and under the water, and considering the dangerous wraiths visible in the water, only a cautious and knowledgeable person such as Dumbledore would find and use it. Left to his own devices, Harry would probably have died in the cavern.

Voldemort's sense of style should also be considered. He had a flair for the dramatic. Without this flair, the Horcrux could be concealed in a shed, a hollow tree, or a chimney. Instead, it's a sea cave on a wave-tossed shore, guarded by ghosts and requiring those who enter to pass a series of magical tests that are reminiscent of the challenges faced in Sir Gawain and the Green Knight.

Answer 3

It's not entirely clear that Voldemort could fly when he hid the Horcrux. The implication from Deathly Hallows is that Voldemort's power of flight is a relatively new development, and a shocking one at that.

"Followed by five, injured two, might've killed one," Kingsley reeled off, "and we saw You-Know-Who as well, he joined the chase halfway through but vanished pretty quickly. Remus, he can--"

"Fly," supplied Harry. "I saw him too, he came after Hagrid and me." (Chapter 6: The Fallen Warrior)

"We saw it," said Bill; Fleur nodded, tear tracks glittering on her cheeks in the light from the kitchen window. "It happened just after we broke out of the circle: Mad-Eye and Dung were close by us, they were heading north too. Voldemort-- he can fly-- went straight for them. (Chapter 6: The Fallen Warrior)

Broomless (or carpetless, etc.) flight is a big deal, with Quidditch Through the Ages straight up saying it can't be done. The Order was being pretty reliably informed by Snape at both heights of Voldemort's power, so their shock at this ability suggests even he didn't know. Would Voldemort really keep the knowledge that he had made a major advancement in magic in his back pocket for decades, even with it's obvious intimidation factor? I would suspect not.

But of course, even supposing he could fly at the time, questions of practicality largely go out the window when talking about Voldemort and his Horcruxes. I mean, he really shouldn't have hidden part of his soul in his mom's house either, or in a castle controlled by his archfoe.

Answer 4

A bunch of comments and answers have focused on the fact that Voldemort might not have had flying capabilities when setting up the cave. While that is a possibility, it seems to miss an important point. Even at a time when we know Voldemort had flying capabilities he still used the boat to cross the lake. From Chapter Thirty of Deathly Hallows:

In a distant part of Harry’s brain, that part connected to the angry, burning scar, he could see Voldemort sailing fast over the dark lake in the ghostly green boat. . . . He had nearly reached the island where the stone basin stood. . . .

Here Voldemort used the boat despite the urgency at hand. (His method of flying is presumably quite fast, as he was able to keep up with people flying on broomsticks.) That he chose to use the boat even in this situation would seem to indicate That flying is simply not an option. This presumably was by design.

Of course, we can’t discount the possibility that Voldemort‘s flying capabilities hadn’t been invented yet by the author when we are first introduced to the cave. Indeed, there is no mention of Voldemort being able to fly prior to the seventh book and all indications prior to that are to the contrary, that human flight is not possible. And even if the author had already conceived of the idea that Voldemort could fly, it would make no sense to write The sixth book dependent on a premise that wouldn’t be introduced until the next book.

Answer 5

The boat was well hidden.

‘Voldemort would have been reasonably confident that none but a very great wizard would have been able to find the boat,’ said Dumbledore.

_{Rowling, J.K.. Harry Potter and the Half-Blood Prince. Pottermore Publishing. Edición de Kindle.}

In addition, Voldemort wanted to keep the ones capable of discovering his secrets to that degree under control, by killing them or keeping them busy time enough for Voldemort to reach them.

Therefore, Voldemort wanted that whoever reached that cave could also reach the island, because then he would drink the potion and be incapacitated, instead of instantly attacked by the inferi.

‘I’m sorry, Harry; I should have said, he would not want immediately to kill the person who reached this island,’ Dumbledore corrected himself. ‘He would want to keep them alive long enough to find out how they managed to penetrate so far through his defences and, most importantly of all, why they were so intent upon emptying the basin. Do not forget that Lord Voldemort believes that he alone knows about his Horcruxes.’

_{Rowling, J.K.. Harry Potter and the Half-Blood Prince. Pottermore Publishing. Edición de Kindle.}

Thus, Voldemort left the boat to allow other people (and maybe himself) to reach the island, in order to trap them there, allowing him to interrogate him if he wanted, or in order to kill a dangerous competitor that might know his most valued secret, the Horcruxes.

Answer 6

Didn't an Inferius leap out of the water to block Harry's summoning charm when Dumbledore asked Harry to go ahead? By that logic, the Inferi would have leapt out of the water and grabbed whoever attempted to fly over the water.

The whole point of the Horcrux is that someone should be able to find it to resurrect Voldemort. So in case the Horcrux needed to be invoked and fetched for his resurrection somebody would have to fetch the Horcrux on his command. Flying was out of question because of the Inferi so he put a concealed boat for his followers to fetch the Horcrux at his direction.

The cave was very well concealed and protected by powerful magic. Surely whoever was capable of such defensive curses took into account that a broom could have been used and Dumbledore knew attempting such was pointless. Also Voldemort was narcissistic and egoistic. He wanted to visit the Horcrux whenever he wished. To Voldemort the idea of not being able to see something that was a part of him was unacceptable.

Answer 7

Further to the other answers, Voldemort needed a second person to come with him to drain the potion at the centre of the lake. Even if he could fly to the centre of the lake (a bit if), it's even less clear that he could or would fly another person to the centre as well. It seems unlikely he'd touch a house elf or a lowly person to bring them across.

Also he probably saw flying on broomsticks as a likely way to get from the sea cliff to the cave for some would be attackers. Broomsticks should be assumed to be available so he's very likely to have cursed an approach to the centre of the lake by flying.