Set sail for the high seas in your Boat and when it returns you will be rewarded.  

Unlock your Boat at the required level and after creating Equipment with the Sea Captain on the Dock, load up your Boat with the Equipment and set sail. Once your Boat returns from the high seas you will be rewarded with Ingredients and Crates.

To create Equipment simply tap on the Sea Captain, the little guy fishing on the Dock to open the tool to create your Equipment. 

The Ingredients (Salmon, Avocado, Saffron, Shrimp, Lobster, Coconut, Pineapple, & Caviar) you will be rewarded with and the amount you receive will depend on the type and amount of Equipment you load your Boat with.

Crate rewards will vary depending on the length of time you are sailing. You will need to claim all your rewards from the Boat before you will be able to set sail again.

You will also need to upgrade your Boat in order to increase your haul!

Once you have tapped on the Boat, you will see an arrow in the top right corner and when you click on that, it will open up the upgrade option. Simple!