Gravity Boost

The Gravity Boost is a power-up for Samus in Metroid Prime 2: Echoes. It helps Samus move and see through the water with ease, and letting her do a triple Space Jump underwater (it actually makes her float, but it does the same job.) It was located in Torvus Bog, at the Hydrochamber Storage Room. When Samus collected it, she had to fight the Alpha Blogg, which is the guardian of the item.

The Gravity Boost has a similar effect as the Gravity Suit in the games that feature it (liquids no longer hinder movement or sight), except the additional third jump that is possible underwater with it being a tradeoff from the suit's additional defense (though the defense gained from the Dark Suit would already be matching the Gravity, anyway). The Gravity Boost also functions in the waters of Dark Aether, however Samus will not sink into them without the Light Suit.

In one cutscene, after Quadraxis's head is destroyed, she used the Gravity Boost to jump away from the exploding head. This is contradictive to the fact that it's exclusively for underwater use.

Strangely, with or without the Gravity Boost upgrade, Samus doesn't "sink" in Dark Aether's poisonous waters, even in areas that would otherwise be deep enough to for her to fully submerge herself when she's in possession of this suit. This prevents obtaining submerged Sky Temple keys without obtaining the Light Suit, making it impossible to complete the game without the Light Suit.