There is free snorkeling on Galapagos’s Isla Isabela close to the port. There is a small path leading to a place called Concha de Perla. The path is guarded by resting sea-lions, and if there are any males, they will bark and may attack. You can climb around them and the female majority will leave you alone.
I went twice. First just stayed in the bay-like area that constitutes Concha de Perla, swimming around, seeing colourful fish. Next I wanted to see more. Sea lions and sharks and stingrays and all kinds of wonderful creatures swim around that area, but you have to go into deeper waters. That involves swimming to the edge of the circular bay, and climbing over some sharp rocks, into the open sea. I had flippers and a snorkel, and I swam for a good 45 minutes in the sea looking for something other than fish. I saw nothing, but when I decided to go back I realised I was lost.
While being lost in the open sea may sound terrifying, I had no reason to panic. I could see the island, just not the entry to Concha de Perla. I had flippers on so could move faster, and while I was disappointed not to have seen any sharks or stingrays, at that point I was glad there were no predators nearby.
After about 15 minutes swimming by the coastline, I found the entry back to the bay and back to land. Self-guided tours aren’t always worth the money you save.
If anyone’s planning a visit to Isabela, this website has a lot more info on snorkeling La Concha de Perla – http://divingthegalapagos.com/the-galapagos-islands/shore-snorkeling-on-isla-isabela, just don’t get lost.