Here is one for the technicality minded.
This is at the marina in Kent.
A middle section of a long run of the floating pontoon has started to accumulate rainwater via fixing holes on the top surface.
The floats are about 1.5m x1m and are about 12 years old and are in good condition. The void is filled with blocks of polystyrene and the whole float is sealed.
The floats have to remain in situ although the decking can be lifted.
I have a theory, what would you do to remove the water that has ingressed, before sealing the offending holes.