I used to snorkel and gig flounder and other species in 4'-10' of water off Cape Cod. Used a broom handle 5-tine gig with a wrist lanyard, hold the gig just behind head and lanyard between thumb and index finger with the lanyard hand, and use the other hand on the butt of the gig to propel - the more length of the gig you could get above the water, the harder and faster you could propel it. I also used a sling spear to snorkel fish in Maui - I think that would be pretty sweet for flounder here too if legal.