A couple of open-air joints across from the water serve up excellent seafood grills a few nights a week at the Gros Islet Fish Fry. They are ultracasual: wait for a plate of barbecued fresh fish, get a few sides, then find a spot in the dark at a picnic table.
Wash it all down with a cold brew or a bottle of sea moss punch. You get a good cross section of local society here.