I can only speak for myself but my boner puddle is barely an inconvenience.

The water molecules next to other molecules of water are drenched but some water molecules like on the edges of wet surfaces are not surrounded by other water and must be less wet than other water.

Water is variably wet depending on its situation and location.

Masturbating over someone makes me think of the last few minutes of a lot of porn where the man/woman is down on their knees waiting for the money shot.

Honestly, a pretty funny mental imagine with these 3 involved.