There is some interesting snorkeling around shallow structure just inside the Shark River inlet, Manasquan inlet, etc., and on almost any jetty when the sea is flat and calm. The stanchions and rubble around RR bridges and roadways like Rt 35 can be fun, but watch out for strong currents. Stay shallow and close to shore, wear gloves, and try to keep in physical contact with the structure you are exploring. The hour of quiet water around peak high tide is best. Don't snorkel anywhere that you have not first carefully observed during tide changes.
Dock pilings and sea walls that are close to the ocean offer excellent snorkeling, when the water is reasonably clear. Beware of boats: use a flag, but don't depend on it. Snorkel defensively and stay out of open water. Stay away from fisherman, and expect to encounter old fishing line and hooks, so carry at least one small sharp knife. Be prudent and alert.
This time of year there are lots of small tropical fishes that came up on the Gulf Stream. I saw many Butterfly Fish, a few damsels and one Blue Angelfish over the past few weks, mostly under docks.