# In Heaven Sent, what was really beneath the waves?

Another rather spoilery question about Doctor Who S9E11 Heaven Sent.

When he first falls into the water, he sees thousands of skulls lying on the bottom of the sea.
Later on, when we find out that he's been here and has died many times before, it's very strongly hinted that those are all his own skulls: when he dies, his skull is all that remains and it falls in the water later.

So... were those all his skulls from his previous incarnations? If so, why weren't there billions of skulls in the water near the end? If not, do we have any indication whose skulls they were? And/or, was the situation on the seabed also "reset to its initial state" regularly?

• “why weren't there billions of skulls in the water near the end?” — I suspect there were, but visibility isn’t that far underwater, and it’s a bit difficult to represent billions on a TV screen. Nov 29, 2015 at 16:17

I'm pretty sure we're actually told in part of The Doctor's monologue who's skulls they were, and I don't think there's any good reason to doubt him at that point:

They were The Doctor's.

Keep in mind, when we see them for the first time, it's early in the episode, and

He had only gone through the cycle maybe a few hundred thousand times (it's not clear how long a cycle lasts, but he had "only" been at it for 7,000 years.)

So the number was still relatively low. Also, it's a really big ocean, there's no telling how many floated and/or rolled away in the interim.

• The confessional dial is Timelord, it is bigger on the inside and there is no limit to how big it can be. Nov 29, 2015 at 14:28
• a quick napkin calculation tells me that 300 billion human skulls takes up about 435 million cubic meters. Our Earth oceans have a combined volume of ~1.3 billion cubic kilometers. There's a lot of room in an empty ocean. Nov 29, 2015 at 15:42
• Hm, OK. I was imagining a great big heap of skulls around the castle, but of course in a billion years these things can drift off a bit. Plus some of them could even have decayed a bit (if Timelord skulls are subject to such mundane processes as decaying). Nov 29, 2015 at 17:18
• @MrLister over time gravity would forcibly redistriubute them across the sea floor, plus I believe we see a pair of them floating up to the surface at one point, where they're at the mercy of any currents. Nov 29, 2015 at 18:28
• "I'm pretty we're actually told" - vanity, in a SE answer? :-o Nov 30, 2015 at 22:53