BC's is a classic of the unpretentious tropical bar genre: plastic chairs, a rickety pier, cold Belikin straight from the bottle, and a view west over the lagoon that makes the whole enterprise worthwhile. The rum punch is mixed without ceremony. Nobody is trying to impress you, and that is the point.
The sunset here — over open water, without buildings in the way — is the kind of thing that makes people extend their stay. Arrive about half an hour before dark, claim a spot on the pier, and order two rounds before the light goes.