[…] for the submerged shafts of the sun split like spun glass, move themselves with spotlight swiftness into the crevices- (10-14)
Nothing can hide from those "shafts of the sun," which tells us that everything is plain to see, even if it's hiding in a crevice. So, all the life-stuff answers must be there too, ready to be illuminated by us.
bespattered jelly fish, crabs like green lilies, and submarine toadstools, slide each on the other. (23-25)
In life, everything is kind of sliding "each on the other," just like these sea creatures. Sure we may want our space, but we also need to recognize that there's a lot of other stuff out there looking for the same thing. But here, all the sea creatures are content and accepting of the way things are.
[…] The sea grows old in it. (40)
Folks keep wondering about this final line because there's something about it that really captures all the life-stuff. The sea, or life on a more symbolic level, continues to "grow old" and endure despite the odds often being against us. Here there seems to be something eternal about life and the sea that we continue to be fascinated and inspired by.