I recently discovered that both my forward and rear water tanks (on each side) had sender units for the gauge, but only the forward ones were attached.
This got me thinking, because we have an issue, which a lot of Lagoonies seem to suffer, in that our gauge shows 3/4 when the tanks are full or at least the rear tanks are full.
With this new information, that the water tanks gauge is taking its reading from the forward tank, I did a little comparison and sure enough, on our boat anyways, the rear tank fills up slight earlier than the forward. Guess its a little higher in the boat.
So with Lagoon water tanks being prone to splitting and overflows being prone to blocking.