Not sure of any places in Stone Harbor. I have been down there a couple times and usually end up going to Strathmere, but that doesn't break for crap anymore. I would say 59th st. pier in OC would be the next closest, but that is just getting even further from SH.
the place i always go to in the general area is 18th street and 21street in avalon. gotta wait for the life guards to leave though. During lifeguard hours i know theres 80th street nun beach and i think 18th but that could be wrong cause they were working on the beaches there a little while ago. Your best bet is just wait until the lifeguards leave and go to the 21st area unless the surf is worth fighting off the crowds during the day.
No guards between 12 and 15 in AV... but it's nothing special. Crowded and lots of idiots out there. Unfortunately there isn't much else... 30 is trash, 110 isn't much better. Cape May has some good beach breaks