The adventures of the crew of the spaceship Ertak continue.
The Terror from the Depths by Sewell Peaslee Wright
"Commander John Hanson challenges an appalling denizen of the watery world Hydrot."
The similarities between these stories and the later Star Trek TV show are even more evident as we learn that Commander Hanson was "...one of the youngest commanders the Special Patrol Service had ever had...", just as Capt. Kirk was the youngest captain in Starfleet. Makes you wonder if Roddenberry ever read these stories when he was a boy.