As Hana approaches the edge, she may or may not notice that the silt stops and the floor becomes swept-clean rocks
Caroline nods her agreement with Steven
I think that's a good idea: we can see pretty well, but fresh water isn't known for its clarity and no amount of fancy eye configuration is going to help if the water is just too full of junk for light to even get through. Granted, we can always teleport back to the beach but if one of the kids wanders off it will not be fun.
Keiko hasn't had luck finding anything - it's likely the group's noisy entrance scared every away fish within a mile. Caroline's concern is not unfounded, either: with the hatchlings playing in the silt, visibility is beginning to drop.