Blue Brinstar Boulder Room
|Blue Brinstar Boulder Room
|Blue Brinstar Double Missile Room
|Blue Brinstar Energy Tank Room
To get onto the invisible platform without Gravity Suit, you'll need to start in the previous room and jump through the door transition, possibly with a walljump off the side of the platform.
The fastest way to exit this room is a well-timed shot to the door, which will allow you to just run through.
If you're in the water without either Gravity Suit or Hi-Jump Boots, you can use a crouchjump-downgrab into the doorframe when the water is at its highest.
Alternatively, you can use a running spinjump timed so that you can walljump below the door when the water is at its lowest.