The room is primarily filled with water, hence the name. Navigation of the water is made more dangerous on the first visit due to the Gravity Feature not being authorized. Whether this room has always been flooded is unknown, though the damage to it, and presence of human architecture in the submerged area imply that it was not.
On the first ledge, and at other points in the room is a ventilation shaft in the wall, through which thick green vines or roots have burst and grown over the room. These vines end in the water. A railing for a sliding platform is present here, although the platform is on the other end of the room. Also under the water are three port holes and noticeable cracks and rubble on the floor. Vines are found growing out of two of these, two more remain intact, and a Whipvine covers the last; when killed, the tunnel can be entered (see the Items section below). A grating for the hole lies on the floor directly under the Whipvine, suggesting it emerged from the tunnel and knocked the cover off.
At the back end of the underwater tank is a grate directly in front of Samus, and a side room with a faint red light and a sensor. When Samus shoots the sensor, the sliding platform moves to the front of the room. Samus can then use it, but has to shoot three Whipvines in Search View while on it to avoid them knocking her off the platform. Once she reaches the rightmost ledge, she is free to continue onto the next room.
- Missile Tank 1
- Samus must kill a Whipvine underwater, and then roll into the small tunnel behind it. The tank is here.
- Missile Tank 2
- Requires the Speed Booster and Gravity Feature. On her return to the BOTTLE SHIP, Samus can now run at full speed through the gate on the far wall underwater, to reach this tank.
- ^ Metroid: Other M Premiere Edition, page 67: "The hall in the next room is a long water-filled tank. Drop into the Skultera-filled water and fight your way past the Skulteras and Frondanas in the water.
Turn left near the end of the tank just before you reach the grate at the end. Locate the glowing plate in the small niche and shoot it with your Charge Beam to activate a sliding platform overhead. As the platform slides left across the long hall, begin backtracking to the left side of the room. Destroy the Frondanas on the ceiling as you go before you reach the now-active platform. Hop onto the platform and ride back across the hall, this time over the water, to the hatch on the far end."