Sebastian is a great place to go treasure hunting. The McCarty Museum on Rt.A1A in that town is built on the site where survivors from the Spanish galleons came ashore after they were shipwrecked in 1715. Their ships were laddened with gold dabloons and pieces of eight and it all dumped into the deep blue sea that will be in front of you as you look out from the ramp behind the museum. In this century salvagers have become famous hunting for the treasure from those ships.
I know I'm not likely to find any but its so fun to go through the museum and see all the salvage and understand what it was and where it came from. Gold doesn't break down so any that is found is as good as the day it fell into the water but silver is a diferent story. The closest I have come to actually owning a cob (coins produced like these were) is from a coin dealer in Ft. Lauderdale but if I'm likely to find any on my own it would be here.
A real good time to treasure hunt is right after a hurricane because it sturs up the water and forces something that's been in the sand out at sea to change its location and come into shore. Lots of people already know that so expect crowds.
Its best to go to the museum and buy some of the paperbacks written by salvagers such as Kip Wagner. Relax on the shore with a nice cooler full of coke and read them and dream. You may even see salvagers at work. We noticed a large barge sifting something in Sebastian Inlet when we were there.
Don't go out and buy equipment until you have read most of the paperbacks because it's not easy and it is dangerous. The treasure is out in the reefs that are so sharp they caused the ships to sink in the first place and there are sharks in those reefs also. And worse of all the state wants their fair share. You need a permit to hunt treasure in the water and it costs. Treasure hunting on the beach is free.
If you really want to get into it go to the Mel Fisher Museum also in Sebastian. They will sell you a permit but everything related to that museum is very expensive. Its another great place to find out about the treasure though.