Lake Clark is 42 miles long, 1056 feet deep, and covers 128 square miles. It's the sixth largest lake in Alaska. Nearby Lake Iliamna is the second largest lake that is entirely in the U.S., after Lake Michigan. 

There are numerous smaller lakes and ponds throughout the park and preserve. The larger lakes are; Telaquana, Two Lakes, Turquoise, Twin, Portage, Fishtrap, Caribou, Lachbuna, Otter, Snipe, Kijik, Lower Tazimina, Upper Tazimina, Kontrashibuna, Hickerson, Crescent, Pickeral, and Summit.