Not a good idea. In Maine lobster can only be taken in traps, not on scuba. The lobstermen are pretty protective. It might be a good way to get yourself shot. There's bound to be a "lobster in the rough" place nearby. Actually, they may sell them at the camp store in season, if I recall correctly. I've only stayed on HI after Labor Day but I seem to recall a lobster tank and signs indicating that. (Heck, there's a campground on Southport Island that will cook and deliver them to your campsite. "Room service" lobsta!)
(Even in Massachusetts, where they can be taken on scuba, you still need a license and can only get one as a resident/property owner. And you can't take them at night as it's too easy then, exactly because that's when they may be wandering around the bottom.)