I'm trying to find the name of the story, and any anthologies that contain it. I seem to remember it involved German scientists trying to find oil by using wormholes, but they end up finding water instead, opening a portal at the bottom of an ocean somewhere?
Secret Unattainable by A. E. van Vogt.
It is written as a series of communications between various Nazi officials. The story starts:
The file known as Secret Six was smuggled out of Berlin in mid-1945 when Russia was in sole occupation of the city. How it was brought to the United States is one of those dramatic true tales of World War II. The details cannot yet be published since they involve people now in the Russian zone of Germany.
All the extraordinary documents of this file, it should be emphasized, are definitely in the hands of our own authorities; and investigations are proceeding apace. Further revelations of a grand order may be expected as soon as one of the machines is built. All German models were destroyed by the Nazis early in 1945.
The German scientists invent a steerable wormhole, and one of the uses is indeed to recover oil from distant planets. However the machine is in some sense sentient and is driven mad by the twisted views of the Nazis and it connects to some point underwater.
The dark planet, from which the city had disappeared, was abruptly gone from the orifice. In its place appeared another dark world. As our vision grew accustomed to this new night, we saw that this was a world of restless water; to the remote, dim horizon was a blue-black, heaving sea. The machine switched below the surface. It must have been at least ten hellish miles below it, judging from the pressure, I have since been informed.
There was a roar that seemed to shake the earth. Only those who were with the Fuehrer in the steel room succeeded in escaping. Twenty feet away a great army truck stood with engines churning—it was not the first time that I was thankful that some car engines are always left running wherever the Fuehrer is present. The water swelled and surged around our wheels as we raced up the newly paved road, straight up out of the valley. It was touch and go. We looked back in sheer horror. Never in the world has there been such a titanic torrent, such a whirlpool.
The water rose four hundred feet in minutes, threatened to overflow the valley sides, and then struck a balance. The great new river is still there, raging toward the Eastern Sea.