Yeah, the deep ocean does it for me as well... had a dream once when I was young that I was floating in the ocean, a dozen or so meters under the surface, and it was during a storm, so the waves could be seen and felt, but it was relatively calm where I was, and near pitch black. Small rays of light made it through, but nothing else. There was this sensation of movement around me, like being blindfolded in the middle of a busy intersection, and with the roaring of the rain and waves, my senses were really confused... and then there was a crack of lighting, and below me, so large that I couldn't see all of it even if I were to turn my head all the way around, was a gigantic squid.
It's tentacles were thick like skyscrapers and thrashing cumbersomely, just this colossal weight crashing through the water and sending waves with it's passing, and directly forward and down was the centre of it, and instead of a beak, there was two gigantic, black, round eyes, and a low moan, echoing like a whales song, almost human, but impossible to mistake for it.
No, I never read Cthulhu in year 5 -.- I just got an early start on my unique flavour of fucked up, apparently.