There is water along this route and at Crater Lake itself.
This trail begins at Andrews Lake just south of Molas Pass on US 550. The whole trail is highly used to Crater Lake, so there shouldn't be any issue route finding (unless you are doing a winter snowshoe or skin) to Crater Lake. The trail to Crater Lake is just under 5.5 miles, but it just seems to be longer, I don't know why, it just has that feeling to me.
Take several switchbacks and gain some elevation before you hit the first meadow. You'll seem to repeat yourself as you climb a "step", go into a meadow, and go back into the forest.
At about mile 4.5, you'll come to a large area with many downed trees due to a microburst several years ago. During the run, if you have forgotten mileage, know this, that once at the downed trees, you are close to the lake.
After the downed trees, you'll descend into a small valley and then ascend the other side. On top you'll come to a large pond which you'll skirt. Continue to skirt the pond and come upon Crater Lake.
If you have arrived at Crater lake and decide that, that wasn't enough... good, there are options. One is to simply explore the area, it's beautiful. Or, for those who want some quad and lung busting elevation, continue on to North Twilight. You can find the description for the run up Twilight here: Crater Lake and North Twilight