Description from the publisher:
"Global warming threatens Vanuatu. Many islands are in danger of disappearing under the sea due to rising waters. Players will therefore have to unite to protect the islands by building dikes. However, the interests of one are not necessarily the interests of others."
Vanuatu: The Rising Waters, the first extension for Vanuatu, adds an option (as part of the Build action) for players to build dikes to protect islands from rising waters. Water can reduce a player's points from houses, submerge an island completely, and even end the game early with no winner.