In early rituals, the location of the rites had to be right. If every element surrounding the ceremonies was not just so, all Hades might break loose. The location of the ship had an effect on how acceptable the honors to Neptune were. A rite performed off certain capes (for instance, those with temples on them) would work best.

Apprentices had to be instructed in the behavior that was acceptable and unacceptable. As a later Ancient Mariner discovered to his grief, the rulers of the deep frown on anyone who kills an albatross. Obviously, the sailor who isn't so certified is little more than a landlubber. Ask any shellback. The pollywog simply hasn't been around--and a worse stigma for a sailor is hard to imagine.