1. An aquatic douche, any person(s) of unsavory personality or taste (also consider a foul sense of humor, or downright idiotic demeanor).
2. A tomato sandwich, garnished with avocado and zucchini. The scuba douche is oftentimes enjoyed on rye bread, although it is not unheard of to be served the "S.D." on pumpernickel.
Lummox No. 1: "Hey, Martha, check out that scuba douche in the window! I'd like a slice of that douche."
Lummox No. 2: "You're such an asshole, Harvey."
'Scuba douche' is not a slang term. it isn't something you imagine would be said in Atlanta if you're from Chattanooga or Montreal. It is a completely fabricated concept, and should be disregarded as such.