Great Bay Temple is infamous for its confusing structure and long length, but these speed tricks help it go along much faster, whether just to complete or to get all fairies along with it.
It is possible to complete the entirety of the temple without turning the switches to change the water direction or create water pumps. The water direction normally needs to be switched to reach 2 green rooms. To skip the turnkeys, one must reach these rooms without changing the water direction.
2 Water Pumps normally need to be activated to continue; the yellow one at the start and the green one at the boss door. Both of these can be skipped with 4 distance hovers.
To get to the first green room, one must simply hover to the aclove that leads to its door. This is just above the map chest, so it can be hovered to directly.
To get to the second green room, the one right before the boss door, one must use the titular "Turnkey Skip." There are 2 ways to reach this room. The first is to hover out of bounds and dive to the tunnel that you normally exit the room from. The second is superswimming against the current into the room, which is impossible (or very near so) to do in real time, and must be achieved through slowdowns, whether through TAS or pause buffering.
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.
To reach the waterfall room for the fairy within before getting ice arrows, one can simply do 6 height hovers (with an angle change) and grab the ledge as Zora Link. Not recommended if low on explosives, as you usually come back to the waterwheel room with ice arrows, depending on what the goal is.
There are a few ways to get the boss key without fighting Gekko. The first is a simple jump from an ice arrow platform to the window it is in. Another method includes a precise side roll, which proves to be difficult. The most popular method is a Zora long jump directly to the window.
Using Hovering to get out of bounds, it's possible to skip the boss key, and nearly the entire temple. The most efficient place to do this is in the tunnel connecting the main room to the waterwheel room.
Though this method is very fast, it can be extremely difficult and has also been obsoleted by the simpler bomb clip method. Damage yourself down to 1/2 heart and grab a fairy before entering the temple, then position yourself so that you will grab the ledge right in front of the torch in the first room as you are damaged by the bomb. The frame for getting damaged is the black one after the 7th flash. Once the fairy revives you, simply do a recoil flip into the loading zone.
This is currently the fastest method of skipping the Boss Key.
†-On the Japanese version you can turn Link around while putting on the Zora Mask. However on the English versions, you will have to take a second to turn Link around before putting on the Zora Mask.
This method is not as precise as the 2 explosive method, but can still be tricky to learn. Stand on the dark line in the middle of the square on the floor relative to the video. Align c-up so that the top of the game clock is to the right of the waterwheel. Do 3 straight height hovers (timing of a wall hover). After, do a backflip holding back and right until you are underneath the tunnel (use a chu to end the hover there). Sidehop straight left and end the hover once past the tunnel. Sidehop straight left again, releasing all buttons. Once in the water, hold left to stay in the water and rise a small bit, then swim towards the boss loading zone, which is a giant window facing away from the main room.
This is a safer and generally easier version of the 5 explosive method. Simply do 4 hovers up facing the waterwheel, then so a sidehop hover to the right to clip through the pipe. Do a backflip hover under the tunnel, then 2 sidehop hovers left so that the left side of the B button is aligned with the edge of the waterwheel. Then simply sidehop left, hold back, then hold up-left when you land in the water to swim directly to the loading zone.
Opening the first door from about the middle to align this. The camera will be off upon entering, so pivot straight left and immediately shield drop a chu. It will go all the way around and hit the bubble underneath (the fairy noise will go off if wearing the Great Fairy's Mask, so that's how one can ascertain it was hit). An easier but less flashy method is to align straight forward in the middle of the platform and shield drop a chu after its fourth flash.
Go to the left of the original platform and hookshot the ceiling, pressing B immediately after and holding towards the platform to jumpslash on top to reach the fairy immediately. Alternatively, one can stand on the corner near the tektite then hookshot and hit B without a direction on the control stick to recoil on to the top.
To do the chu roll, stand relative to the location of the video and align c-up in about the same way, using parts of the HUD to make the alignment more consistent (Aligning the top of the game clock with the left side of the orange part of the floor works well), then shield drop the chu. This will have it go along the wall and under the seesaw to break the barrel with the fairy inside.
If lacking explosives, one can get the fairies without hovering at all, yet still skipping the use of fire and ice arrows. A Zora roll jump with jumpslash is enough to make it from seesaw to seesaw with proper timing, then a long jump to the turnkey allows access to the tunnel to hookshot the fairy chest. For the second part, a much easier way of getting the fairy in the underwater barrel is to align with the back of the seesaw and shield a chu after its second flash.
To skip ice arrows, a chu recoil a slight bit to the left of the aclove from the peak of the elevator is enough to make it. Afterwards, a quick hookshot will reach the other chest from the moving platform below. The first chest can also be gotten with near frame perfect hookshotting but the risk greatly outweighs any time it would save in real time.