Three-Tooth Lake is a lake in the Shadowlands. Its name comes from the three small islands it encompasses and is a play on the word trident. The three islands are:
The lake and its islands are home to many unique creatures in the Shadowlands. It is only here that Keen will encounter the fiery Berkeloids, the underwater dwelling Sprites, Schoolfish, and Dopefish, as well as the hazardous Underwater Mines.
Two Council Members are trapped in the lake area, awaiting rescue. One is found on the Isle of Fire and the other in the Well of Wishes, making Three-Tooth Lake a required area to visit in finishing Commander Keen's adventure in the Shadowlands.
In order to enter the lake, Keen will first need to obtain the Wetsuit from Miragia. It's interesting to note that written on the piece of paper containing Tom Hall's original sketch of the Dopefish are the words, 'Need Trident Power Ψ to go underwater', implying that more supernatural means were originally needed to enter Three-Tooth Lake (or at very least the Well of Wishes), and possibly inspiring the lake's name as well.