Air boat 1 launched for survey. Survey began air boat shut down w/4 EEs aboard. Attendant notified; notifications made; plan formed to launch second AB for retrieval. Air boat launched. When they arrived to AB 1, AB 2 quit running. Mayday called; Sup. Instructed 2 EEs to get marsh master w/ paddle boat, plywood & rope to retrieve EEs. Marsh master overheated; EEs were removed.