no water comes out but it'll quite often start dripping out onto the rear left wheel.
The side boot trim has an access panel that can be removed by unclipping it as if you were changing the rear lights.

With the cover off, move the sound deadening to one side.

Pull the wiring bundle out and you will find a foam package. Unwrap it or pull the foam back.

This is what you will find, the connectors come apart.

Take a length of heat shrink tubing (10mm to 12mm inside diameter) and slide it on 1 end.

A little dab of superglue on the male end should discourage it from coming undone again.

Pop them back together.

Slide the heat shrink tube over the joint until it's central.

Heat it with a hair dryer or hot air gun. Don't melt everything.

Once it has shrunk, it won't be coming apart again.

Push it all back inside the car and replace the access panel.
Test it and the squirter should work properly.