Oceanus — Philip R Benge

Alun Reece is now the captain of his own small freighter, but it is not freight that Admiral Michaelson wants him to carry, no, it is an industrialist whose son has been kidnapped and Alun has been contracted to find and rescue him. Unfortunately, this journey takes him outside of the Solar System and in to a series of adventures, both in space and under waves of the planet Oceanus, with the risk of death always present, for him, his crew and the people on Oceanus. It cumulated in a battle against two evil enemies, with the outcome loaded dangerously against him.