My boat came with a piece of material with snaps along one side. They snap to the deck just below the forward edge and the sides of the center hatch. You can then open the hatch part way. The material extends aft of the hatch a bit. It keep any water coming from forward or from the sides. We often use it at sea in moderate conditions. It also works at anchor, but won't work in a heavy downpour. Oddly enough it's probably more effective when there's some wind, to help the rain blow past the open aft side.

In a sense it's a junior version of the nice mini-dodger in the pic you posted, Tom. I could take a picture of it but hopefully my description suffices.

Great series about Martha's Vineyard, Tom, I noted it for a future fall or off-season trip.

Max