No. . .

He's only mentioned the naked beach once.

In "Serenity", Zoe mentions getting a real bath, and he says, "That would be great. . .a couple days off. . .you with the bathing, me with the watching you bathe. . ."

Then in "Ariel" when discussing how much they'd stolen, Mal says, "enough to take us wherever we want." Zoe says, "Someplace with a beach?" and Wash says, "Maybe a naked beach?"

Wash loves his wife and thinks she's the most beautiful creature in the 'verse. That's one of the many ways he expresses his desire.