The only way to access the pristine clean water of Crater Lake is via Cleetwood Cove Trail. The trail is popular because it leads to the boat dock where all the boat tours begin.
It is a steep trail with switchbacks drops down about 700 ft within one mile. Ther are multiple benches overlooking the lake if you want to catch your breath or just to enjoy the scenery.
The lake is filled by only snowmelt and precipitation, and there is no inlet or outlet, Crater Lake is one of the clearest lakes in the world (a record clarity of 142 feet was recorded in 1997). With a maximum depth of 1,943 feet, it is also the deepest lake in America and the ninth deepest on earth; the clarity and depth combine to create the intense blue color, the bluest blues I have ever seen.