Lychee,

Hope you get this as I cannot post on chit chat lounge (long story). Many of the "lakes or ponds" are protected. You may need to contact the local water management district, I think this is the correct website: Southwest Florida Water Management District . Do not do anything on your own, there is wildlife (snakes, alligators, etc) in these bodies of water. Also, for the bad news, if what you are calling weeds is NOT an invasive species, you may be out of luck. There were earlier threads about other bodies of water with "weeds" where nothing has been done because these are natural vegetation.
Hope this helps.
VT