The boat channel

draft

The so-called boat channel runs south out of Tatiman Passage, parallel to the shoreline. There is a similar channel running north out of the passage along the Nutiran shore.

The channels may be the result of action by what is termed a "longshore current".

This is the natural path of water to escape the reef, it runs along the shore until such a point where it can find its way off the reef in a natural channel 90 degrees to the beach.

Think of it in typical beach terms where you have longshore flow of water parallel to the beach, and rip tides where the flow is out to sea perpendicular to the beach.