Swimming is also one of his hobbies.
During the "friendly algorithm" Dr. Cooper states something like I'm waiting until we have to get into the water(b4 that he and Leonard talk about Sheldon learning swimming of the net without ever entering a pool)
-I don't think "lisp" is accurate in describing his speech anomaly. "Impediment" is probably closer.
-- That's correct. The substitution of R-sounds with W-sounds, like Elmer Fudd, is called rhotacism (which see). A lisp is when you replace S with a TH.