Sunlight

Oxygenate Water (also known as Sunlight) is the spell that Mumbo Jumbo uses in Jolly Roger's Lagoon. Because Jolly Roger's Lagoon is mostly underwater, Banjo and Kazooie's medium-sized air bar is not strong enough to keep them alive while swimming underwater. Instead, when they give Mumbo a Glowbo, he casts a spell on the entire lagoon by using the sun to "oxygenate" the water - allowing Banjo and Kazooie to explore underwater without needing to return to the surface for air.