A Blue Lum is a type of Lum which is found underwater in all versions of Rayman 2 except for Rayman Revolution, in which they are replaced with air bubbles. They contain oxygen, which Rayman needs when he swims in bodies of water he cannot resurface to, otherwise his oxygen meter will run out and he will drown. Some stay and provide an unlimited amount of oxygen. Others disappear for a while once they have been collected.
Blue Lums in Rayman 2 are said to represent the origin of all life, and the very first breath of a creature's life. When a creature is born, it is given Blue Lums to keep until the day it dies. As he is the only being Polokus did not dream, Rayman may or may not carry his own Blue Lums in this way.
Usage in other games
Blue Lums also appear in the Game Boy Advance version of Rayman 3, Rayman: Hoodlums' Revenge and the Game Boy Advance version of Rayman Raving Rabbids. In these games, the Blue Lums resemble Tings, and they do not give Rayman air; instead they briefly grant him the Super Helicopter power, much like the potion he receives from the Musician in the original game. In Hoodlums' Revenge, they simply act as fuel which sustains the Throttle Copter – a separate pick-up which allows Rayman to fly via a mechanical apparatus attached to his head. Rayman must quickly collect Blue Lums in order to keep the Throttle Copter in the air.