Spear Fishing Practice

When I was a young lad I went spear fishing with a friend, and we found ourselves on the edge of an unsettling underwater "cliff" that went down, apparently forever, into the darkness.
Being the chicken that I am, I immediately imagined scary leviathans coming up from the depths below, and I nudged my friend to swim back to shallower waters.

A few weeks ago the memory came back from some reason, so I started this. Only, this time, the main character isn't an easy to scare little boy.