When I was a kid, my father ran the pool at the college where we lived. They used to teach scuba classes there, but quit because of the damage to the pool and the pool deck.
Most of the damage was from from students dropping weights on the deck, which would crack the tile. (cracked tile(s) would cause cuts on peoples feet. I for one found this out exactly that way with a large cut on my foot once). Dropping of tanks and other gear also didn't help any.
As someone above said, get soft weights. That will help the problem a lot.
But I gotta love the "leave the spear gun in the garage" comment.