While originating in Star-Spangled Comics in August 1948, Captain Mark Compass eventually graduated to the big leagues in Detective Comics in 1954 for a near two year run, keeping some of Batman's back pages warm.
A nautical detective hired by a Penny Steamship Lines to ferret out various criminal crews, Compass made a living as a roving troubleshooter. If you served on a ship in that fleet and saw Compass heading your way, better believe trouble would be following along. Eventually he met fellow detectives of Detective which indicated he was of Earth-One.
He wasn't the first in this genre of heroics. Lt Commander Don Kerry of the US Navy was also assigned to investigate suspicious goings-on at sea, and did so as a contemporary of Earth-Two's Batman although in the pages of Adventure Comics. Kerry focused primarily on a main antagonist in the form of a criminal known as El Diablo, before branching out in his tales. While Compass was the lone wolf in his adventures, Kerry had a sidekick in Red Pennington... definitely more serious than another sidekick of the day in Slam Bradley's buddy Shorty Morgan.