How to fill and seal this hole?

[brookswildlife]

The previous owner cobbled together scraps of wood to make a base to mount his seat. It seems he didn't build it high enough and instead decided to drill a 2 inch hole right through the boats bench seat to make it fit. The wood was all rotted and I removed it all as I have no use for it. What is the best way to fill and seal this hole? Spray foam and sand it flush? My intentions are to paint the interior of the boat and install foam padding over the seating areas.

 

[Stand Up]

I can't tell what size of hole it is, however a button cap available at most hardware stores should work.
https://www.homedepot.ca/product/paulin-1-2-inch-hole-button-plug/1000127129

 

[airshot]

If that is an aluminum surface, just cut out another piece larger and rivet into place.

 

[mirrocraft16]

If its wood, automotive body filler works great for filling wood. Mix in some chopped fiberglass for some added strength.