Most docks are posted "No Fishing" for a reason. as has been mentioned, the docks are used by the local kids for swimming and snorkeling. Wet Willy's feeds the fish on a regular basis. Therefor it's kinda like shooting fish in a barrel.
If you want to fish it is best to hire a guide and a boat or go out to the lagoon. The river (or cut) is a good place to fish, especially at sunset. The local kids line up there and tight line fish. It is a real education and experience.