Don B.
Yelp
Cleetwood Cove is the one and only (legal/realistic) way of getting to the water's edge at Crater Lake. And if you're visiting during summer months, let me assure you - you want to get to the water's edge.
The road to Cleetwood is only open in the summer, once the bulk of snow has melted. There is a parking area across the road from the trailhead. If you have tickets to ride the boat (advance purchase required) you exchange them at the mobile unit in the parking lot for your actual boat passes. Then descend. The trail is a little over a mile, and you get a lot of vertical feet in. of course the way down is easy (on everything except the knees) and can take at least 30 minutes. The trail itself is mostly dusty, with stunning views of the lake through the trees (see pics).
Once you get down to the lake level, there's the boat access for boat tours. Also just past the boat access is a little rock outcrop that's prime real estate for jumping in to the crystal blue waters of the lake. Protip, you don't need to have boat tickets to come down here. Also, the water is cold AF, but if it's even slightly warm, and the sun helps, then it's worth your while to jump in. There's nothing comparable to swimming in the deep blue of one of the world's deepest, and clearest, lakes.
Things to bring - water, and plenty of it. Especially if it's hot. A towel, a change of clothes (unless you don't mind hiking in your wet swimsuit back up), some snacks, and a GoPro. Swim, sun on the rocks, and take in the sheet stunning beauty that is Crater Lake. Get plenty of good time in, because the trudge back up a mile of dusty switchbacks awaits you on your return trip.
This is a must stop for visitors... even day trippers. The round trip, with swimming included, is only a couple of hours. And there's nothing like being at water level in the depths of the crater. BOOM!