What is a boat and a boat list?

Once you reach around chapter 3, you'll receive a boat with your country's flag just left of the lighthouse. This is your access to visit other players' islands. When you tap on this boat you'll find a list of the players you may visit, which consist of the small group of players that the game grouped with you, your FB friends who play, and your club teammates. You can exchange bushes with anyone on this boat list. If you are not in a club and share a coffee in the detective lounge cafe (available after level 14), this group minus the ones in a club, are the players who can see your coffee and share their drink with you.