"The Night Sea-Maid Went Down"

by Brian Lumley
originally published The Caller of the Black, Arkham House, 1971

Bernard Jordan's been working on an oil rig in the North Sea.  But he's quitting.  And here's why:

The Sea-Maid had a lot of problems - equipment malfunctioning, schools of man-eating fish, and they kept turning up what they thought were fossilized starfish, but turned out to be something else entirely.

Those last caused crewman Joe Borzowski to flip out.  Later he quit, sending Jordan a letter explaining that there are ancient god-monsters in the sea and the earth, and he thinks they've disturbed one.

A sea-quake rocks the Sea-Maid, and it begins to collapse.  As it goes down, Jordan sees a gusher of blood coming up from the drill and shooting from the sea into the sky.  He knows what they drilled into.

Jordan is the lone survivor of the rig's sinking.  He's not going back to sea....

This is a pretty minor story, being basically a kind of mash-up of elements from Lovecraft's "The Temple" and "The Shunned House."  Lumley sets it up pretty evocatively - making the weak payoff all the more disappointing.