...or should we say "barely" costumed for this one? The Shark!
This guy--seen here proudly displaying his own logo--had the nerve to run in AMAZING MAN COMICS circa 1940 where the book's title character was sometimes being drawn by the Sub-Mariner's papa, Bill Everett! Yes, Ol' Sharky was a bargain basement clone of Subby without any of the angst or one lick of backstory. Just as Namor has his quirky feet and ears, however, our hero here had...for no apparent reason mind you...webbed feet and hands. He also insisted on wearing a big blue mask...and little else.