There are only 2 boat services from Copacabana: 8:15 and 13:30h. Those 2 boats are the same that return from the island, so you can only do a daytrip if you leave in the morning. If you have to take the 13:30 boat, you will have to stay overnight there.
Tickets cost 10 Bs (1.2 USD) one way, 15 Bs (1.8 USD) return on the same day.
If you stay overnight, will have to buy the return ticket when you take the boat back (and it will cost about 15Bs!).
Boats take 1 and 1/2 hours to the south point, and make also a second stop in the north before returning to Copacabana.
Tickets are sold anywhere in Copacabana.
You can see some of the regular "lanchas" loaded with people leaving Copacabana for Isla del Sol. Some of them seemed pretty top-heavy with most of the passengers up on top. I understand it is around 25 BOB for a round trip to the island.
I took a bus from Copacabana to La Paz. At one moment the bus stops. In the beginning I thought it was just a break but all the locals went to a small ferry. The bus got on another one.
The boats put us on the other side for a bit of money.
Two other tourist on the same bus didn't follow the locals and just looked in a shop. They had to rent another boat. It had cost them more then 10 times the price than for us.
Vehicles are not allowed on Isla del Sol, so you must either walk or take a boat to get around. The island is about 21 km long and 8 km at its widest point. There is a trail that runs the length of the island along the center ridge. Parts of it are over 4000 m (13,123 feet) in elevation. We walked the ridge trail from Chincana to near Yumani, a distance of about 4 miles.
The picture shows the ridge trail near Chincana. You can see the Rock of the Puma, Mesa Ceremonica and the Chincana ruins in the background. You can also see a piece of the trail back to Challapampa on the right. See a separate travelogue for views along the ridge trail.
It is very reasonable to hire a private boat to take you from Copacabana to Isla del Sol. That way you can conveniently stop in several places. Captain German charged 450 BOB for a day and a half. That included the ~2 hour trip from Copacabana to Challapampa with a stop at Huancani to drop off the luggage. He then picked up the luggage at Huancani the next morning and picked us up at the Yumani Pier afterwards. After a stop at Pilko Kaina, it was back to Copacabana. I also tipped him 50 BOB for his good, reliable service.
The blue frame and seats on top of the cabin allow you to sit on top and see everything well. It was a bit chilly up there, so don't forget your jacket. You may sit inside if it is raining. See also a separate travelogue for pictures on the boat trip.
Most people like to sit on top to see better. However, if it is raining or too cold, then there is a comfortable cabin with big windows in which to sit. You can see the Copacabana shoreline through the windows in this picture.
A mock version of the real thing - has an engine and the peddles are there to fool you. Nevertheless, it is romantic.
Captain German has two outboards on his lancha, which gives you some extra speed and a backup motor in case one goes out. Copacabana is in the background.