You should do o.k. there if you take your time. Google the tide schedule for that area and learn when the low tide will be out. Get there just before low tide, make sure you turn down the sensitivity of the 250 until it doesn't go crazy in the wet sand, turn your discriminate down low also or you won't find gold and then hunt just above the wave line on the shore. That is a good way to water hunt without being in the water. When the tide is out, you are standing on ground that is normally knee deep to waist deep when people are wading and swimming in the Gulf at full tide.
The Key has produced some good items. You just have to work hard to find them. Make sure you take a good shovel or better yet a beach scoop if you have one!
Good luck!!!!