1A boat — a general term for a small watercraft. Often used in compounds (e.g. ボートレース 'boat race') where the exact type of boat depends on context.
週末にボートレースを見に行った。
I went to watch boat racing on the weekend.
湖でボートに乗って景色を楽しんだ。
I rode a boat on the lake and enjoyed the scenery.
台風でボートが岸に打ち上げられた。
The boat was washed ashore by the typhoon.
2A rowboat — a small craft propelled by oars, often referring to a recreational rowboat or a competitive rowing boat.
週末に友達と手漕ぎのボートで釣りに行った。
On the weekend I went fishing in a rowboat with friends.
公園の池でボートを借りて二人で漕いだ。
We rented a rowboat at the park pond and rowed it together.