While staying in Mazatlan, we decided to participate in the Stone Island Tour. We had received free tickets from taking a tour of the Pueblo Bonito Emerald Bay Resort. We were told that they would pick us up at the hotel at a certain time.
When we went to the lobby, we were taken to our "taxi." It was a pickup truck with wooden benches and a canopy in the back! They took us to the dock where we boarded the boat.
The tour itself consists of two main parts. In the first part, you travel in an open-air boat from the dock through the Mazatlan harbor to Stone Island (which isn't actually an island; it's attached to the mainland). The tour guide on the boat was very fun and informative. They take you by caves, past all of the cruise ships in the harbor, past the lighthouse, and past some rocks that are colored white from bird poop (at that point, they advise you to get under the covered part of the boat). The ride lasts about an hour, during which time they also take your order for lunch. The boat is very nice, with bathrooms and even a bar. After touring the area, they dock at Stone Island and the second part of the tour begins.
Once you arrive at the Stone Island shore, you board these wagons that are pulled by tractors. They travel over dirt roads to the other side of the island. Along the ride, you see some very poor areas. At their shelter/restaurant area, they serve you your lunch and schedule your activities. You can choose from snorkeling, banana boating, and horseback riding. We chose the horseback riding and it was truly amazing! The horses are small and easy to ride. You don't have to know anything about riding, as they all follow the leader horse. They take you riding along the beach, through a forested area, and then back to the restaurant.
Since we didn't choose any of the other activities, I can't say first hand what they were like. However, we did hear from many people who went on the banana boats. They told us that when they were a short ways from shore, the guide made them fall off. As the banana boat is very slippery, they could not get back on. They had to swim to shore (not a very far distance). Beware if you're not that good of a swimmer. After a few hours on the island, they take you back to the dock by boat, and back to your hotel by a truck/taxi. The tour is fantastic and I highly recommend it.