A lake was a large body of fresh water. Lakes were common on class M planets.
Betazed had two notable lakes, Lake El'nar and Lake Cataria. (TNG: "Dark Page", "All Good Things...")
Balfour Lake was a body of water located on an M class planet. (TNG: "Attached")
Lake Tahoe was one of the largest freshwater lakes in the western United States of America. It was located near Reno, Nevada, where it shared a border with the state of California. (DS9: "It's Only a Paper Moon"; VOY: "Vis à Vis") Lakes George and Como were also located on Earth, the latter being in Northern Italy. (VOY: "Coda", "The Swarm")
The Lake of Lusor was a body of water located on Qo'noS, the Klingon homeworld, near the Kri'stak volcano. (DS9: "Rightful Heir")
Lake Yuron was one of the few bodies of water on the planet Vulcan. (VOY: "The Disease")
Four holographic Starfleet officers, including Weiss, covered theirselves in a lake during a hunt in a Hirogen training facility. They shot the two Hirogen from inside the lake. (VOY: "Flesh and Blood")
The Axiana Lakes, on the planet Talaxia, were several large bodies of water connected to each other and were located near the Godo Mountain Range. (VOY: "Homestead")
Lake Armstrong was a large artificial body of water on Earth's moon. (Star Trek: First Contact)
A large lake existed on the planet Ba'ku and was home to at least one species of fish. In 2375, Lieutenant Commander Data uncovered a cloaked Federation holoship hiding on the lake. (Star Trek: Insurrection)