You can also hike from Copacabana to Yampupata and hire a boat for 70 Bolivianos (about $9 USD) for the 20 minute crossing to Isla Del Sol (Yumani). The hike is pleasant, passes through some quant agrarian coastal villages, and supports the economy of the towns outside of Copacabana. If you want to avoid breathing diesel fumes there are some places along the hike to Yampupata where you can hire a local villager to row you across to Isla Del Sol.