I grew up on Hamilton and swam in it pretty much every day during the summer. Not too many places on it are clear enough for diving/spearfishing. Below Blakely Dam is nice.....but cold, cold, cold. Wear a wetsuit. It's also pretty clear on the other end by Carpenter Dam.
Its been a few yrs since i dove in Hamilton but the water is better now than ever. You're not gonna have the visibility of Ouachita but its not to bad. Lots of docks with brushpiles under them
You gotta be careful though there are so many boats on it you better be under a dock or in a protected area cuz nobody on Hamilton even knows what a dive flag is...!!!!