[1] In Superhero Comics of the Golden Age, Mike Benton wrote: Everett recalled that when a boyhood friend suggested the idea of Hydroman to him, I thought it was utterly preposterous.
[3] In 2008, Hydroman appeared in the Dynamite Entertainment miniseries Project Superpowers; here he was referred to by the nickname "Hydro", possibly to avoid any conflicts with Marvel Comics who by now had a supervillain character called Hydro-Man.
According to Jess Nevins' Encyclopedia of Golden Age Superheroes, "Hydroman defeats spies, an alien invasion led by the Great One, Yellow Perils, fifth columnists, the Phantom, the Alchemist, and the Native American murderer Black Bird".
When exposed to sunlight, Jay could fly at the speed of light, leaving a rainbow-like trail in his wake which he could shape and control (much like Green Lantern's ring power).
At some point after World War II, Hydroman and Rainbow Boy were each trapped and imprisoned in the mystical Urn of Pandora (along with scores of other heroes) by the misguided Fighting Yank.