Underwater Algae is a crafting part in Dying Light. It can be used for Boosters or for making various weapon upgrades, among other blueprints. It is speculated that as a booster, Underwater Algae provides 'oxygen' to the players so that they can stay underwater longer.
Underwater Algae can most commonly be found submerged in salt water areas, such as Harran's inner harbour. Underwater Algae also glows at night, making it much easier to locate.