CONTINUOUSWAVE

Q1: what is the frequency among all owners of a 210 MONTAUK that water is accumulating under the cockpit where the portable head is located?

BACK STORY
[In my recently acquired (apparently used) 210 MONTAUK (of unspecified model year and age)] water will accumulate under the cockpit where the portable head is located.

My inference is this water comes from the deck because I have noticed that the water color [that accumulates under the cockpit where the portable head is located] is the same [color] as the blue soap that I have been using.

I observe a seam that goes all around the cockpit. I plan on [removing the existing caulk from this seam and] recaulking.

There is no statistically significant data about the frequency at which owners of a 210 MONTAUK report they observe accumulation of water in the area under the cockpit of a 210 MONTAUK where the portable head is located available on this website. You might get one or two anecdotal reports about this situation.

Generally in a boat water tends to accumulate in the lowest areas where the water can flow to under the influence of gravity. Generally one might expect that the typical orientation of a boat hull will be to be slightly down by the stern. However, if the boat is transported on a trailer on the highway, it is entirely possible that due to descent of grades on the road that loose water in the boat could flow toward the bow. You should consider this possibility in deduction of where the water that is accumulating might be coming from.

If you want to eliminate the accumulation of water in the sump area, you need to figure out where the water is coming from. If your hypothesis that the water comes from the cockpit deck, the only way to eliminate that is to cover the cockpit deck when the boat is not in use, and to drain any water that accumulates from using the boat when you put the boat away after use.