He draws Castiel closer, tilting his head into the kiss and holding him close. 'I love you' isn't really a thing that the Winchesters say easily, no matter what. So he's always glad of the little things that Castiel does and allows him to do in return that show rather than just tell.

The kiss goes on for a while before Sam pulls back, smiling down at him. "Come on. Let's get dried off and go to the bedroom. There's still a lot that I want to do to you before we sleep tonight."