The series premiered in 1968*. Stopped in 1974 after 72 issues, but has been revived several times since then.
The title character is the mutant son of a human sea captain and a mythological princess from an undersea kingdom, and his given name is Namor. He is a superhero with most of such characters' abilities plus a full, amphibious adaptation to the sea.
The full title of the series for the first 24 issues was Prince Namor, the Sub-mariner.
* The character first appeared in 1939, and he has over time starred in several other series of his own such as Essential Sub-mariner, Namor the Sub-mariner, and Sub-mariner Comics.
(presenting the front covers from 6 random issues)