Bottom coat?

 I’m building a passage maker and I’m a little confused about painting below the waterline, I might leave it in the water for the entire summer. What product should I paint the bottom with, thanks!

   You will need to use a marine anti fouling bottom paint.  otherwise when the water warms up you will have barnacles and growth on the bottom.  Do not use top side paint below the water line
 

   Thanks, do you recommend a brand?

   Look at the Pettit brand.