>Longer boats and ships somehow create less drag through the water, so a longer boat makes some sense.
Longer people do too. Michael Phelps is 6'4".
When I did triathlon, I took a tri swimming class. We were taught to glide as much as possible and ROLL from one side to the other like a screw through the water. One arm is like a shark's dorsel fin getting ready for the next stroke, the "stroke arm" is actually in front of you like you're putting your hand into a letterbox on a door to lengthen your body in the water while you ROLL onto your side and GLIDE through the water. Very little kicking because you want to save your legs for the bike and run.
I used to love going to the pool and gliding past 20-something men who were paddling their arms like crazy trying like hell to beat me...and then being able to continue laps when they were huffing and puffing on the edge of the pool.
So satisfying for the kid who was always chosen last for dodge ball.