If your Facebook friends have the My Tribe application installed, then you can visit their islands, and you can visit theirs! Sailing to each others' islands will help both your tribes to grow and prosper.
To sail to a friend's island, find their Facebook picture on the list at the bottom of your game. You can use the arrows to scroll back and forth through the list, and there is no limit to the number of friends you can have listed in My Tribe. Your friends are displayed in descending order of their level in the game.
Click on their picture and select Yes to sail to their island. Once you're done there, click Go Home to return to your own island.
Sailing to a Friends Island[]
Sailing to your friends' islands benefits both your tribes. Comb their beach for Stork Feathers, shells, bird guano and other resources. Both you and your friend will get all the items you find added to your Supplies list. Every day you can collect one Stork Feather per island that you visit.
Fertilize a friend's farm to keep it in excellent health, or to revive a wilted crop. Click on Fertilize, and then click on the farm you'd like to help. Your own Facebook photo will appear above the crop and let your friend know you've helped them out.