Did you know that it's espcially important to put lids on marine fish tanks? That's what I have heard, at least. Supposedly it's becuase ocean fish have no concept of "the surface" of "the water".
Think about that, really. To them, organisms surrounded by saltwater, thriving with viruses, bacteria, plankton, algae - we might as well be living in space to them. There's nothing up here, except when there is. Puddles, lakes? Might as well be little planets to their own.
Now, take this further. Actual space? That's space 2, to a fish. Imagine that.
A lot of posts consider the cosmological horror of the deep. I'd love to see more consideration for the horror of the surface to deep things, espcially when they realize their equivalent of outer space has a space all it's own, infinitely unknown.