Best Practice for Obtaining Area of Intersecting Plane & Part

Hello! I need to be able to calculate the area of where a plane intersects a part. See pictures. The blue shaded areas are the planes in the picture. Need area of where the intersection is between the plane and boat hull. I had tried to create a sketch on the plane and then create lines that form an enclosed space but it does not seem to be working for me. I cannot "grab" the edge of the intersection to place a line. Is there a way to find the area of where a plane intersects a part (in this case a boat hull) that's a better practice than what I tried? Thank you.