when in NYC on the weekends- boats to hit are the Garloo (Captain Hank) Aqua Explorer (Captain Dan) or Tempest (Captin Tom) out of Freeport - there are also beach dives at Beach 8th Rockaways, Oak Beach, and Ponoquogue Bridge.... only at slack tide.
There are lots of great dive shops and buddies - look at anyone of the dive groups[- Sea Gypsies, Broadway Divers, Long Island Network Divers.... LIDA