The Mist Marsh is made up of three main areas. The Outer Marsh is the large crater exterior leading up to the crest of its rim. It is not sure how high it rises, but it may be no more than fifteen feet. The second part is the rim descending to the bottom of it. Since the mist never seems to dissipate, the interior may be lower than the exterior. The Inner Marsh is the bottom bowl of the crater filled with dead trees and the Zarn's ship. The Marshalls used the higher ledge at the ending point of the Mist Marsh to lure Fred, the Zarn's robotic dinosaur, to get hit by lightning.
The Mist Marsh was first discovered by Rick and Will Marshall while charting the Land of the Lost. Encountering the Zarn's Ship, they explored it and earned the Zarn's ire, getting an android sent to investigate them. They have since stayed away from it except in a time they investigated the Zarn for damaging the gravity of the Land of the Lost. The Mist Marsh also seems to have escaped the effects of the cataclysm that rocked the Land of the Lost. It is unknown what happened to the Zarn, but the Mist Marsh also managed to similarly trap Captain Ruben Van de Meer and his ship, the Flying Dutchman.