I'm assuming you're talking about Florida, and the answer is Nope. Not even in wet sand technically. On the beach, all lands below the mean high-water line are state sovereignty submerged lands.
Cant get into the water along treasurecoast at all and that includes your coil, state parks that border the ocean is up to park ranger ask before you detect, federal land is strictly off limits, 99% of the other beaches will allow you to hunt in the water with no problems at all, I have been doing so for almost 15 years.
There is a small group of Key hunters here - but dont get caught on treasure coast in water - they might be in a good mood and just tell you to get the heck out
but there have been guys that got machines taken fines and in a few cases got brought down to the station (usually these are ones that stand up for their rights)
been a while since i heard of someone being taken down---but years ago - i heard stories of guys posing as fishermen and dropping a guy over with tanks
and getting caught