Middle Lagoon, previously known as Tanja Lagoon, is an Intermittently Closed and Open Lagoon (ICOL).
Most of the time it is closed to the sea.
Occasionally after periods of heavy rain the sandbar is breached and the lagoon is opened out to the Tasman Sea.
The lagoon then becomes tidal for a time until the bar is again closed by the waves depositing sand.
The lagoon begins to fill again with high tide wave surges and rainfall.
While the lagoon is tidal water activities are restricted to periods of higher tidal variation as shallower areas like in front of the tents are exposed until the bar closes and the lagoon fills once again.
Swimming at the lagoon mouth on the incoming tide is glorious at these times.