From the Module description:
The High Council of Tritonius has put out a call for doughty adventurers to retrieve a lost document bearing terms of peace to the Border Kingdoms of the dry-skins. Apparently, factions exist in their organizations which are not keen on peace, and these may be responsible for the lost message. Go figure what the dry-skins want, they're all crazy anyway. So the mission sounds easy, but why are you the only volunteers...
So the Council gives you a map, points you off in the right direction and gives you instructions not to return until you have found the message. Easy as pie. They have even thrown in a dry-skin to make sure you don't do a bunk. That's all right, adventure and money lie ahead... Here is the twist, though. To be more specific in instructions, find a sealed 3' long waterproof tube in a six square mile area and deliver it to air-breathers over dry land...
AD&D 1st Edition for FOUR Characters of 4-6th Level Equivalents