Hopefully you’re able to find the source of the water easily.
BTW: Not sure where you dock but I saw a boat just like yours as I was driving East on Montauk Highway yesterday.

 

Yes I'm just off Montauk Highway across from the High School
Removed all the tile today the floor is fiberglass no signs of water, need to dig a little deeper

 

Probably fiberglass over plywood sub floor.

 

Yes that's what I'm thinking and it separated. Ill be checking for that tomorrow or monday

 

I have resisted the urge to tile the floor in the head as the only way to get access to the shower drain and its hose is to cut and opening in floor in the head. In live with the carpet and use a small decorative throw rug.

 

I cut a hatch in the floor and dug out all the foam down to the hull to expose the shower drain. I recarpetted the bathroom and the access cover to the new storage area.

 

Carpet in Bathrooms? My wife is having nightmares right now...

 

Give her time ... she will get over it.

 

had the same prob with my 390,the caulking pulled apart in the shower under the curtain guide.Dug out the old
placed new all ok

 

About 15 years ago i installed marble tile in the head which held up quite well, Till now found a small soft spot in the head floor . Guess i'll be ripping it up stay tune! View attachment 84314

Finally did something about the soft spot, Found the foam under the floor to be compromised added three cans of spray foam back under the floor put down 1/4 " cement board and retiled the floor I'm happy Now!