It'll almost certainly be fresh water that'll be coming in from a deck fitting. Common sulprits are:-
Stantion bases
Mooring cleats
Deck fillers
Genoa tracks
Hatches and windows (gets in behind the frame and runs down between the 2 skins)
Get your hand in the saloon high level cupboards and see if the tops of any are damp.
As Bob say's above;
use an aqua vac to suck all the water from the matrix frame.
If the water is clear next check the area around the water pump make sure the water is turned on an pressurised. Feel around the pump and filter with your hand or a dry tissue. there is a problem with the seals on some water pumps that form the valves. the symptom for leaks on th efresh water system in the pump funning randomly when no water is being used. Usually the middle of the night just as your dozing off!
Check the hot and cold pipes from the clorifer. Especially the red hot pipe in the last 400mm before it enters the cylinder. Little pin holes in the red pipe some times appear. check the inlet pipe to the water tank. The clips can sometimes lose there grip on the pipe. Check the sender unit and the inspection cover. Do this with the water tank full to the brim.
On some older Bavaria's the deck fittings on the sugar scoop are bedded in silicone mastic, and the bolts are just sealed where they touch; eg the dive ladder, filler caps etc, the binnacles are too, so check the sealant around all these. White silicone has a life of 5-7 years in marine applications due to the UV and harsh environment. Even the very best only last 10 years.
If you replace them go for a butyl sealant, or a polyurethane. Do not use polysulphide or bituminous mastics. Sika flex has a good web site to help.
Hope this helps
Ant
PS perhaps we should do a find that leak check sheet for the forum........ ?