Considering the nature of One For All and the way it is passed from hero to hero, not all of the powers contained within are immediately accessible. Float was one such ability, and it was imbued into One For All by Nana Shimura (Mie Sonozaki and Stephanie Young), All Might's former mentor. The power allows the user to at first levitate, but with greater usage and skill, it becomes a powerful means of transportation and evasion.
Deku first activates this skill when he instinctively uses it to save his friends and get away from Tomura Shigaraki (Koki Uchiyama and Eric Vale). Even though the quirk is called Float, it really is just the ability to move in the air and fly in any direction at will with incredible speeds. Deku uses it both defensively and offensively –- the ability to fly can be used to dodge attacks, rescue friends and innocents, or deliver devastating offensive moves.
Of course, being in a city populated by both heroes and villains, a lightning-fast mode of transportation is always great for response times.
