The left side 舟 is a picture of a boat — oracle-bone versions show a hull with plank lines. 船 added a sound component and became the everyday word, while 舟 retired into poetry and radicals.
同舟共济 'crossing in the same boat' is the Chinese ideal of solidarity — even enemies row together in a storm. Zheng He's 15th-century treasure ships 宝船 were the largest wooden vessels ever built, a century before Columbus sailed with a fraction of the fleet.
Boat 舟 on the left — this is the BOAT you board.
The Dragon Boat Festival 龙舟节 races long narrow boats to honor the poet Qu Yuan — one of the world's oldest continuously held sporting events, over 2,000 years running.