Because the load zone for the boss room is below and somewhat near the entrance room, it is possible to reach it with an out of bounds recoil flip.
This alternative spends more time setting up all the way into the corner to make the recoil flip more lenient.
It's possible to skip turning the underwater turnkey by getting onto the waterwheel as Goron and rolling to the other side.
Target the wall in the corner, tap sidehop, and angle Link with an ESS turn or c-up as shown in the video. Dry roll into the water once the platform is down, then turn left, transform Goron, and roll across the wheel with the visual cue shown in the video.
After clearing the Tatl text, tap up on the control stick and immediately shield drop a chu. Run forwards a little bit to get around the wall, then shoot the skulltula. Put on the Great Fairy Mask as soon as possible, then follow the same setup used without fairies (see above). The second fairy sometimes doesn't directly into Link; if it begins circling instead, go for the roll across the waterwheel, then put the Great Fairy Mask back on on the opposite side to get the fairy to come to Link.
Four distance hovers span the gap.
This is a Zora high ledge grab out of a dive from a platform. Hold A the entire time. Dive off, hold the control stick opposite the direction Link is moving, and time a B press right when Link enters the water. Ideally, Link will fly out of the water and land on the platform. Other times he will stay too low and grab the edge of the platform.
This grants access to rooms that are only meant to be accessed after changing the first waterwheel's direction.
Link will void out if he's ever swimming in water that doesn't have ground beneath it, so this setup aims to keep him above the tunnel the entire time.
To load the room, transform human, get in the corner between the loaded water and the wall, crouch stab right to push Link into the water, and superswim until the room loads.
Original video by Gigo
Load the waterwheel room and align Link to the left of the dark line on the wall. This is directly underneath the only OoB location in the tunnel, so it won't work on a different wall. Do 3 wall hovers up, making sure to get an angle change. On the next hover, hold up to stop your momentum, and end your hover once under the tunnel. Once there, turn around (use map cursor to help) and do distance hovers back until the background turns blue. At that point, dive with a full bottle or trade item and you will land in the tunnel. The current will take you into the room as it is reversed from what it would normally be.
This requires hovering five times and unlocking the camera before transforming to Zora and grabbing the ledge. Hovering is extremely laggy here, so timing the camera unlock is awkward.
Link will void out if he's ever swimming in water that doesn't have ground beneath it, so this setup aims to keep him above the tunnel the entire time. See the video below for demonstrations with and without collision view on.
See additional notes by Imbued.
Shoot the ice arrow from right next to the ladder. Immediately after shooting the arrow, press A to exit first person and hold the control stick to make Link turn towards the ladder. If done correctly, he will begin grabbing the ladder before the cutscene starts. Hold up during the cutscene to climb the ladder.
While swimming from the central room to the map room, begin holding target. Dive out of the water where shown and bonk the wall. This will make Link face the direction he was facing when you started to hold target, which is now facing the platform. Hold forward after bonking to move forward and grab the platform.
Aside from transforming and using the hookshot, it is possible to reach the map chest from the red turnkey door with a frame perfect Zora high ledge grab. This can be backed up with a transform ledge grab.
This video shows how to hover to the upper door from all three of the nearest platforms.
Line up with the center of the room while using the Zora barrier to kill the three underwater biobabas. Turn in the water and dive to either land on the lily pad or dive directly onto the platform to kill the final biobaba.
This video shows the slightly slower method using one lily pad.
There are several ways to get the boss key without fighting Gekko. The fastest is a jump as Zora. To set up the jump from the biobaba door, target and shield turn up-right; if setting up without that initial angle, target the wall that the biobaba door is on and shield turn down-left or target the wall behind the two pots and shield turn up-left. From here, hold target until the end of the jump. Get to the area behind the pots, then hold up/up-left to make Link run up-left, as opposed to sidestepping left. Roll shortly before reaching the edge and let go of A so Link jumps instead of diving. If Link gets stuck bouncing instead of grabbing, hold R and mash B until he does a jump attack to land in the window.
The video below demonstrates the jump described above, the ice arrow method, and the Zora long jump method.
Dive off the platform and use a Zora high ledge grab (frame perfect B press in this case) to grab the upper platform. From here, use the icicle to clip through the wall as human by target walking forwards and a little bit into the wall.
Whether you want to head to the door as Zora or human depends on what form you plan to use in the next room. Both options are shown in the video below. As Zora, carefully get onto the axle, walk back onto the waterwheel once it turns, and jump to the door. As human, walk over the tip of the waterwheel as it turns, then jump to the door.
Sink and target the wall in the corner shown, then turn and target away from the wall. Shortly after the tip of the waterwheel disappears on the top of the screen, begin swimming. Dive out and jumpslash to land on the waterwheel. Head to the door using one of the methods shown in the main video above.
Recoil flip towards the alcove when the platform is at the top of its range. This is useful as a backup for the long jump strat above.
This is the faster option, but the jump to the turnkey platform is precise.
This option is slower but easier than ascending the room as Zora. Backflip onto the top of the first seesaw, then roll and jumpslash to the bottom of the second seesaw. Link must have space to roll for this to work. Shoot the ice with a fire arrow, then jump to the turnkey as Zora.
This is useful for glitched categories that hover to the seesaw room exit from the map room and need to collect both fairies. Because the position setup in steps 1-3 relies on a diagonal notch shield turn and diagonal notches are notoriously variable between controllers, some runners use different position setups that allow them to use other diagonal notches. If the setup below doesn't work well for your notches, check other runs to see different setup ideas.
If you hookshotted to the chest immediately after the bombchu exploded, then the bombchu fairy should fly into Link during the sidehops in step 8. If there was a significant delay between the bombchu exploding and hookshotting the chest, wait at the chest to collect the bombchu fairy before proceeding.
To skip using ice arrows to get to the fairy chest as intended, use one of the two options shown in the video below:
Use a Zora high ledge grab to grab the platform and skip using the ice arrows. Be careful not to dive off the starting platform with too much speed, as doing so will put the dolphin dive too close to the turnkey platform and make a bonk likely.
Four distance hovers span the gap.