MacFadden-Bartell released eleven Aquanauts adventures between 1970 and 1974. All were credited to Ken Stanton, who was actually the prolific Manning Lee Stokes, about whom you can learn more here.
In addition to the many mystery novels he wrote under his own name, beginning in 1945, Stokes also published men's adventure fiction in the John Eagle: Expeditor, Nick Carter, and Blade series, among others. The Aquanauts were packaged by Lyle Kenyon Engel, who was also responsible for the Chopper Cop books.
With that much experience, you can imagine the Aquanauts was a pretty solid series, and on the basis of the second novel, TEN SECONDS TO ZERO, from 1970, it was. I don't know if other books featured other Aquanauts, because there's only one in his book: William Martin, better known as Tiger Shark.
As a member of the United States' elite Secret Underwater Service, whose existence is known to only a handful of men, including the President, Tiger and his one-man sub KRAB are sent deep behind the Iron Curtain to find out how the Soviets are destroying American nuclear submarines. It turns out the only man who can really stop the attacks is a Russian scientist who wishes to defect to the West, but only if Tiger can break into the palace where the scientist's wife is behing held and bring her to safety.
Stokes creates some suspense in scenes of Tiger disarming underwater mines and the final assault, and adds a sexual touch in the hero's Bondian seduction of two strangers--very "love 'em and leave 'em." Neither the violence or sex is explicit, however, and TEN SECONDS TO ZERO, which gives nice supporting parts to Tiger's boss and to the U.S. President, could have been a fairly decent film too.