Once this suit is acquired, it makes it so that Samus has normal physics underwater, so she moves as if she were above water. This is the only suit that is skipped in most speedrun categories, as it is not required for anything other than 100% completion. In most cases where the Gravity Suit would normally be required, alternative strategies exist that make it unnecessary. This includes the entirety of the Crashed Frigate, which is skipped in most categories and is only required in 100% speedruns.
Additionally, having Gravity Suit increases your damage reduction to 20%.