You have to unlock the Ken/Samantha sharing route. Then RNG when Ken and Samantha are fucking talk about how Ken has never learned to swim. Then go to the pool and pay money to rent the pool the whole day.
Yeah he's not bringing it up for some reason. I'm already Day 85+ and it's still the same dialogue. So I accepted his offer, took the photo, didn't start the sharing route with him (I think it's Anna so I didn't accept), accepted his offer to buy groceries, and completed Samantha's hacker, beach, and sex scenes. Am I missing something here?