Oxygenate Water

From the Banjo-Kazooie Wiki, the largest Banjo-Kazooie info resource.

Oxygenate Water
Game	Banjo-Tooie
World	Jolly Roger's Lagoon
Color	Yellow
Use	Allows Banjo to breathe underwater

Oxygenate Water (also known as Sunlight) is the spell Mumbo uses in Jolly Roger's Lagoon. Because Jolly Roger's Lagoon is mostly underwater, Banjo and Kazooie's medium air bar when underwater isn't strong enough to keep them alive. Instead, when given a Glowbo, Mumbo Jumbo casts a spell on the entire lagoon by using the sun to "oxygenate" the water - allowing the player to explore underwater without needing to breathe.