I wish you all the best on your adventure. If detecting is allowed, why not bring both detectors? If only one and you can or intend to get into the water, the AT Pro.
FYI if this helps, I typically find more good stuff in the water than the dry. In fact, I find the best goodies at waist deep or deeper. Keep in mind the height of the water when people swim, as it may vary depending on time of day or season. My advise on a new spot is to pick an obviously busy section and try detecting it. If it is clean of bottle caps, pull tabs and coins, then it may have recently been hit by someone else. If that is the case, you have to either try for deeper targets or move to a place less obvious or beyond where they stopped (up or down the beach, deeper, shallower, etc). I know one person who prefers cleaned up beaches, as he feels it enables him to get the at the smaller gold such as lady's rings, earrings & chains with less junk or shallow coins in the way. My preference is to be on a place that has lots of junk and then clean out everything. To each their own.