You perform the Sail a Boat action normally, but now if you land your Boat at a Dock with a regular enemy Boat then the enemy Boat is returned to the rightmost open spot on its Clan Mat (there is a maximum of 2 stacked Boats per spot). However, if you land your Boat at the Chieftain Boat’s Dock you DO NOT undock the Chieftain Boat.

Your Deploy Settlers and Explore with a Settler Action

Any time you add Settlers to an Island, you have an opportunity to attack the enemy’s Settlers. If you have more Settlers than the enemy’s Settlers (they may be 2 different colors), return 1 enemy Settler to its rightmost open spot on the enemy’s Clan Mat (there is a maximum of 2 stacked Settlers per spot).