The website is accurate: campsites are primitive, there is at least one boat ramp, there are two islands when the water is high, and there are several picnic tables scattered over the islands.
The boat ramp we took was more than a half mile from the island. The turn-off from the highway wasn’t marked as a boat ramp, we just took the only road we could find that led down to the water. It’s a pebbly dirt road, and not great for small cars but we made it in my sedan. There were two or three primitive camp sites on the way down to the boat ramp that aren’t mentioned on the website, by the way. It took close to an hour for us to paddle over to the island, though admittedly we were not expert paddlers. The lake has a very slight current but it wasn’t a problem.
The website says that Yarnell is two islands when the lake is high and one when its low. Our visit was in late July of 2020 and the water was high at that point because there were two islands. The southern one is bigger and sticks up 30 or 40 feet out of the water. It’s got steep angled rock-cliffs on 3 sides but the north side has a sort of rocky beach where you can put your boat and there is a footpath that starts near there which winds all over the island and leads you to all the different campsites.
The campsites show that effort was made in establishing them in the past; each picnic table has a tent pad that is a pebbly area with the pebbles held in by squared logs. When I was there the sites were overgrown with weeds (I didn’t mind, I liked it). Many of the sites also had fire rings with cooking grills that could be rotated on or off the fire. The picnic tables were made of a sturdy concrete.
The smaller island is the one we stayed on because it was less overgrown and smaller (we didn’t want much of a climb with all our gear). There are o lot two campsites there and it is a lot more open. Since it’s primitive, the openness makes it a bit awkward when you need to find a place to “take care of your business” so to speak, especially when you’re trying to put it where the rain won’t wash it into the lake. There’s a couple spots that work, but it’s challenging. I assume it would be a lot easier on the big island.
The wildlife I saw was a variety of birds (including 2 bald eagles!) and some adorable but VERY bold round fat mice who explored our equipment and left little “presents” inside the boat. 💩 💩 We hung the rest of our food out of reach on a tree branch and had no problems with the mice getting into it. Also there were very small bees (or maybe wasps??) that were very insistent on swarming our tuna and I got stung twice. It wasn’t a problem for me, it was just a bit itchy. But fair warning.
At night, there are a few lights along the bank, but they don’t impede the view of the stars. The view of the stars was amazing. The Milky Way was bright and also I was able to see the comet that was passing by at the time.
There’s a great place to swim on the northern side of the small island that has a rocky shelf thigh deep in the water where you can hang out and stack rocks or jump off out into the deeper parts of the lake. The water surface is warm down to a couple feet (in July), and underneath is cold. I have very fond memories of the time I spent here and I hope to come back someday!