Look what I found - problem?

[JohnC]

What year and model boat and what is it's history?

It almost looks like someone glassed down another layer of roving inside of the bilge. I imagine if someone did that with poly resin and without prepping the existing glass then it would eventually delaminate and look a lot like yours, can't tell without seeing more.

Can you pull it apart enough to see what's under it? whatever it is needs to come out anyway. Under it you will find fiberglass stringers properly tabbed into the hull with healthy looking tabbing or else major delamination of the stringer/hull joint.

I have never seen or heard of a Seacraft with major delamination issues but I guess it's possible.

pull it apart and try to post pics of what's under it.