Suit upgrades are one of the bread-and-butter features of a Metroid game. Unlocking a new suit that allows you to traverse increasingly hostile environments in order to complete your mission is to Metroid as, well, Metroids. In Metroid Dread, there are two suit upgrades to get — the Varia Suit upgrade, which increases your resistance to superheated rooms, and the Gravity Suit upgrade, which not only allows you free movement in water and lava, but also prevents damage from chilled rooms as well.
The Gravity Suit upgrade can be obtained after you acquire the Space Jump and Cross Bombs. You’ll need to head to Burenia, and you can only obtain the Gravity Suit by entering via the green Teleportal, located in Ghavoran — you will need to Space Jump across a gap underwater near the southern part of the map. Once you arrive in Burenia, you have quite a long trek south and southeast ahead of you, but the reward is well worth the effort.
The Gravity Suit will aid your progression as stated above for one huge reason alone: free movement in water. You will now be able to Space Jump underwater, which will aid you in obtaining your next, and possibly final, upgrade — the Screw Attack.