Pi doesn't sleep well and in the morning notices RP is restless.
Pi realizes that soon RP will get really thirsty.
He checks the sky for rain, checks the locker for drinking water, but knows these two can't provide enough for him and RP.
He decides he'll haul in the solar stills (flotation devices which convert salt water to freshwater) he put out two days ago. They're full of salt-free water.
He fills a bucket for RP. He feeds RP. It's been a week since the Tsimtsum sank.