The Lake was commissioned in 2250 and is now retired. It is currently serving as the site of a Federation research project. (TOS video game: Starfleet Academy) This data is taken from the in-game Library computer, where its registry number is given as NCC-618. However, during the actual mission in-game, the ship shown has USS Hawking NCC-618 clearly written on her hull. The obvious solution is to 'adjust' the Lake's registy to something very close, hence NCC-616.