are they bronze - they look rusted instead of green - there are a few shipwreck/treasure museums on the east Fla. coast - try and stop in with it
or send them pics - their is a shipwreck forum page here with guys that are experts - I have many bronze spikes/nails from wrecks from Ma.,Ct.,and R.I.
waters - only one with sizable piece of wood has an iron spike
good luck