I hunted Key West last year and did not do very well at all. I hunted the dry beach at Ft Taylor Birch. The beach there is mostly rock, very few places to hunt sand, so I did not stay long. The only other place worth while is Smathers beach. I spent about 4 hours there and found a junk ring and about $3 clad. Smathers is really the only beach there is in Key West area, unless you want to spend a lot of time hopping from one beach to another, as there are a lot of tiny public beaches that you can work the entire beach in under 30 minutes. As far as hunting in the water,it is not advised to even get in the water at Key west. There is a growing population in the Key west area and the septic systems are very shallow due to the corral foundation of the key, so the septic fluid has no place to go but to sea and it accumulates on the Smathers beach side of the key because there is no current to take it away. Ft Taylor Birch is down on the tip and does get an ocean current so the water may be ok there. I didn't want to chance it myself.
If you want to try the beach hop thing, I recommend you go to google earth and look around. If you are not familiar with Google Earth go to google and type in google earth. You will have to install a small application to work. It is totally free. I use it all the time especially when I am going to a new area, it will give you an aerial view of the entire area you want to hunt.
Hope this helps
HH
Digger