Aquatic Avengers Aid All: Sea Devils and Boy Commandos

Just to show that the Aquamen didn't corner the market on all Seven Seas, each of their Earths had a team of underwater agents protecting life above and below the ocean.

On Earth-One, it was Dane Dorrance and his Sea Devils team consisted of girlfriend Judy Walton, her younger brother Nicky and his pal Biff Bailey, Eventually, the acclaim of the Sea Devils led to the creation of the International Sea Devils including Sikki of India, Molo of Africa, Miguel of South America, Petey Eldidge and a lad named Brad from America. Their chief foe and begrudging ally throughout the seven seas was Captain X aka John Payton Dorrance, who was Dane's father.

Years later, the Sea Devils joined forces with time traveler Rip Hunter (along with his colleagues Jeffrey Smith, Bonnie and Corky Baxter) as members of the Forgotten Heroes of Earth-One.

As to Earth-Two, we had Red Torpedo aka Jim Lockhart operate solo with behind-the-scenes support of his fiancee Meg. Biff on this world was an assistant of Lance "Captain Triumph" Gallant. During their adventures, Torpedo journeyed throughout the seven seas saving the world below, while encountering a fascinating array of awesome life forms such as the Femazons, while battling his arch-enemy Black Shark several times. Eventually, he joined Uncle Sam's Freedom Fighters as they prevented the attack on Pearl Harbor to occur on Earth-X, although this cost Red Torpedo his life! 

Other Earth-Two scuba-divers who swam the same seas as Red Torpedo were the Boy Commandos, consisting of Andre Chavard of France, Alfie Twidgett from England, Jan Haasan from Netherlands, Tex and Percy Clearwater Poodle of America. Each of these members corresponded to a youth on Earth-One, in Nicky Walton, Jason Todd, Dan "Brooklyn" Turpin, Corky Baxter, Jonathan Ross and Bertran "Bug-Eyed Bandit" Larvan. Just as Nicky and Corky were junior partners on their respective teams, Jason was the second Robin trained under Batman as his sidekick, Jonathan was the sond of Superman's old friend Pete who quickly became a type of sidekick, while Percy was more an annoyance as a junior reporter working alongside fellow Daily Planet reporter Jimmy Olsen.

Additionally, there were substitute Commandos named Oklahoma, Bronx and Marconi Einstein Edison also from America. Another charter member Brooklyn was born Dan Turpin, of whom his Earth-One counterpart would be a famous Metropolis law enforcement officer. The Commandos' leader was Rip Carter, a time traveling adventurer like his cosmic twin Rip Hunter who repeatedly battled evil dopplegangers of Rip's pals Bonnie Baxter and Jeff Smith, the male and female criminal couple known as Case 13.