Try "Harvey Cedars Marina"
I used to work at Todt Sailing Center in Spray Beach (formerly Furie Sailing), but it closed a number of years ago and the land is now part of Spray Beach Yacht Club.
I believe Harvey Cedars Marina (in Harvey Cedars, about 8 mi. north of Beach Haven) rents sailboats.
You won't find anything over 20' in Barnegat Bay -- it's mostly 4 feet deep. Harvey Cedars Marina probably has beach cats, sunfish, and small dinghies. If you go over to "the mainland" (say, Toms River), there may be some other possibilities.
Island Surf & Sail rents windsurfers, wakeboards, and kayaks and gives kiteboarding lessong; I don't think they have sailboats, but they might be able to give you more accurate information than I have.
www [dot] islandsurf-sail [dot] com