From the cover:
Adventure awaits on the watery world of Yarhfahl, as players join the race to salvage a valuable cargo from the Drenslaar, a sunken star freighter. But will they elude detection by hostile forces long enough to complete their task?
The Drenslaar Quest is a complete adventure for Traveller. This scenario makes use of rules and information presented in The Undersea Environment, a Traveller supplement also by Gamelords Ltd., and Traveller Book 4, Mercenary; use of these supplements is recommended, but not required.