No its just a big bucket that gets filled up every tide , Tom, and then it needs to get out. I think wave action pushes the water in and over the fringing reef, but to get out it goes out the drain ... the pass. North Minerva reef is like that too.
It effects timing too, its real slack tide is about an hour and a 1/2 or 2 hours after published low, which shows you what sort of back up is in there. Some people say 1/2 tide is best for that same reason. I say get there and have a look at the wave at the entrance.