Nisekoi

Nisekoi is a romantic comedy manga series that received an anime adaptation which aired for two seasons from 2014 to 2015.

Raku Ichijo is a normal high school student who also happens to be the sole heir to the head of a Yakuza Family called the Shuei-gumi. He also happens to keep a pendant that was given to him by a girl he met aboard 10 years ago, with a promise made between them to marry once they reunite. However, things get complicated when Raku has a crush on his classmate Onodera, when at the same time he's forced to become a couple with Chitoge, the daughter of the boss of the rival Beehive gang in order to settle their gang feuds.

Episode 5
Raku teaches Onodera how to swim, later also rescuing Chitoge from almost drowning.

Episode 9
Raku finds himself in the wrong hot springs after the signs are switched.

Episode 18
Raku and his friends go to the beach.

OVA 3
Raku visits a public bathhouse. He also visits a mountain hot spring in the second half of the episode.

Episode 7
Haru has a bad opinion of Raku.

Episode 9
Shu wears a swimsuit while helping to clean the school's swimming pool.

OVA
Raku's yukata has loosened.