How is the bottom of a boat look like ?

I passed by a yacht club very often. One of the function of the building are to store and repair the sail boat.

Generally we know how a sail boat look like right ? Most of us only saw the boat float on the water surface. Something like below photo.

Ever question yourself is there any other feature or shape below the bottom ? Me, NO….. I assume it just like sampan, flat beneath the bottom.

Was shock when I saw the complete sail boat when pulled out from water for the very first time.

Can you see the big flat fin look board at the bottom ?

So big surface…. after gaining this knowledge, next time don’t simply ask the sailor to pull his sailing yacht to land oh ! Stuck at the sand than too late to regret