Hi Barry,
when we go to the beach we always lie close to the jetty.
The snorkelling around the jetty is great, this is the only place where you will find rocks & plenty of fish. We usually go all the way round the end of the jetty, not a great distance & there are always hundreds of fish, though not a wide variety.
We have also in the past hired a pedallo boat & gone snorkelling in deeper water but didn't really spot much.
If you're planning any days out, we've found the best places for seeing fish are Paleokastritsa or Kalami.
Hope this helps,
Carol2