Lake Knights are aquatic creatures that first came out in the episode "My Two Favorite People." They guard the bottom of the lake, where treasures lie. First Finn, Jake and Lady Rainicorn go into the lake and try finding the universal translator for Lady Rainicorn. At the bottom of the lake was treasure and the translator they needed. But when Finn got it, many Lake Knights came out of the trench and began to attack them. Finn and Jake were battling them, until Lady Rainicorn came and defeated the Lake Knights.
The Lake Knights look like fish from the bodies and have a giant horn that is a dull pink color on their heads. They have yellow lightsaber-like weapons and little arms to hold them with.