benoa bay is a tidal estuary located on the southeast coast of bali. the estuary is protected by the narrow sandy benoa peninsula which protrudes northwards from the southern tip of the harbour and which closes off the entire southern portion of the estuary. serangan island which is located to the north partially closes the remainder of the estuary except for a one kilometre navigable stretch of water that separates the southern tip of the island from the benoa peninsula. the northern tip of the island is separated from the mainland at high and mid tides by a very shallow straight which is 400 metres at its narrowest point. the entire coastline is protected by an extensive coral reef system that runs continuously apart from a very narrow (200 metre) channel at the harbour entrance at the northern tip of the benoa peninsula.