After you get Fire Arrows in Snowhead Temple, you can gain access to the Great Bay, which will lead you to the next temple.
Unlock a New Item
If you have Fire Arrows, you can unlock a new type of item that is required in order to reach the next temple: Powder Kegs. If you have already done this, skip ahead to the next section: Meet an Old Friend.
First, go to the Goron Village (the same area where you first saw Darmani's ghost after getting the Lens of Truth). Along the north wall of that area, there is a doorway. If the mountain area is frozen over, you will need to shoot a Fire Arrow at the ice that is blocking this doorway.
After the doorway is open, go inside. As a Goron, talk to the big Goron. He will give you a Powder Keg and tell you to use it to open the Goron Racetrack before the keg explodes. Pick up the Powder Keg and throw it to the top of the ramp behind you, then roll up the ramp. Repeat the process until you reach the exit. Carry the keg through.
From the exit, go slightly to the left and forward to go up some wooden steps, then go to the right up the ramp. When the path splits, go to the right, then go through the exit there. In the next area, go across the bridges, walking past the Wolfos. At the end, there are some ramps to the right. Throw the keg up the ramps and roll up the ramps after. At the top, put the keg in front of the rocks in the wall and wait for the keg to explode, or take off the Goron Mask and shoot the keg with an arrow.
After breaking open the Goron Racetrack, go back and talk to the Powder Keg Seller to get a free Powder Keg. From then on, you will be able to buy Powder Kegs from the Goron in the Bomb Shop in West Clock Town, even if you play the Song of Time and go back to the first day.
Meet an Old Friend
Now that you have unlocked Powder Kegs, buy one from the Goron in the Bomb Shop in West Clock Town (while wearing the Goron Mask) or just get one from the guy who gave you the Powder Keg test. Then, when you have a Powder Keg with you, go to Milk Road before 6PM on the first day. Milk Road is southwest of Clock Town. Become a Goron and put the Powder Keg in front of the big boulder at the end of Milk Road and shoot the keg with an arrow to make it explode (or just wait for it to explode). Go past where the boulder was to enter Romani Ranch.
Go into Romani Ranch and find the girl near the middle who is shooting at a poe balloon. This girl is Romani. Go toward the farmhouse and you will notice your horse, Epona, locked behind bars there. After you notice your horse, talk to Romani and she will teach you Epona's Song. Thereafter, you can summon Epona almost anywhere, just by playing Epona's Song.
Go to the Bay or Do Sidequests First
Now that you can call Epona, you can enter the Great Bay that is west of Clock Town. The Great Bay leads to the next dungeon. However, you can also do some sidequests before that. If you aren't interested in doing those sidequests, skip to the Go to the Great Bay section below.
Talk again to Romani. She explains that some ghosts (or aliens?) are going to come to the ranch before the carnival and capture all of the cows. She asks you to practice fighting the ghosts by shooting ten poe balloons while on horseback. Just move Epona, then press B to raise your bow, and shoot at the poe balloons. Be sure to look behind the barn for one of the balloons.
Afterward, Romani asks you to meet her in the barn at 2AM tonight.
Win a New Mask
While you wait, you might want to ride Epona back to Milk Road and go into the entrance to the Gorman Brothers' racetrack. Talk to the brother near the fence while riding Epona. They'll challenge you to a race for 10 rupees. To win the race, make sure to conserve your carrots. Try to allow your carrot meter to fill before using another carrot. Then you can use all of the carrots at the end of the race for a big burst of speed. If you win you get the Garo's Mask, which will be required later.
Fight the Aliens
Before you meet Romani in the barn at 2AM, you should buy a Romani Ranch map from Tingle. You can find him in Milk Road.
When you are ready, if it's still the First Day and before 6PM, you can play the Song of Double Time (play each note of the Song of Time twice) to go to night of the first day. It will be 6PM after you play the song.
Meet Romani in the barn at 2AM if you wish. The ghosts will appear around the ranch at 2:30AM, so go outside and call Epona before then. When the aliens appear, play the Song of Inverted Time (play the Song of Time backward) to slow time down if you haven't already.
Your objective is just to keep the aliens from reaching the barn. You need to ride Epona to do so, or you can roll as a Goron. Just go in a circle around the barn, killing the aliens. They reappear after you kill them, but with time slowed down, they move pretty slowly. They drop arrows, and there is a crate of arrows in front of the barn as well. You can also ride through the bushes behind the barn to get more arrows. The aliens will all disappear at dawn, so just keep shooting until then.
If you successfully prevented the aliens from reaching the barn, Romani gives you a bottle of milk. There are two servings of milk in the bottle. You recover 5 hearts each use. This completes Romani's entry in the Bombers' Notebook.
Get a New Mask
If you got rid of the aliens during the Night of the First Day, then at 6PM on the Second Day, meet Cremia in front of the barn of Romani Ranch. Talk to her to get a ride to town. After a cut scene, Cremia says that you need to shoot the pursuers behind the wagon with arrows. (It's obvious that the pursuers are the Gorman brothers.) Shoot them whenever they yell, because that's when they are about to come close. If they get really close, shoot them a bunch of times until they fall back. You have unlimited arrows during the wagon ride.
If all of the milk bottles break, you won't succeed. But if at least one of the milk bottles is still unbroken, you get Romani's Mask. Wear this to enter the Latte Bar, which opens at 10PM each night. The Latte Bar is in East Clock Town next to the Stock Pot Inn.
In the Latte Bar, you can buy Chateau Romani Milk for 200 rupees. This powerful milk will give you infinite magic power after you drink it, but the effect wears off when you go back in time.
Go to the Great Bay
Now that you know Epona's Song, go to Termina Field and play Epona's Song, then ride Epona to the west side of Termina Field and use carrots to make her jump over the fence.
In the Great Bay, look for the owl statue to the left of where you entered.
Help the Zora
Go into the water and swim to the object beneath the gulls.
Swim behind him and press B when it says Grab, then swim toward the shore while pushing him.
When he falls over, talk to him. When he asks for healing, play the Song of Healing.
Mikau leaves behind the Zora Mask. While in Zora form, you can read Mikau's grave to learn
what you can do as a Zora:
1. Go into the water, then press and hold the A button to swim. While holding the A button underwater, use the control stick to change direction while swimming. You can even jump out of the water this way, in a maneuver known as the dolphin jump.
2. If you have magic in your magic meter, press and hold R to create an electric barrier around yourself. The barrier protects you, and can damage enemies.
3. In water, press B to sink to the bottom.
4. While standing, press B to punch. Press it repeatedly to do a barrage of punches.
5. Hold B and release it to do the double cutters attack. This attack is also known as the fin boomerangs.
Get Another New Mask
The next part is much easier if you have a certain mask. To get this mask, go east from Clock Town with Epona to reach Ikana Canyon. Use carrots to make Epona jump over the fences until you are facing a cliff with someone sitting on top of it. To the right of that cliff, there is a circle of stones. Use the Lens of Truth to see an invisible soldier in the middle of that circle of stones. Talk to him to get the Stone Mask. When you wear this mask, most enemies will not be able to see you.
Get More Bottles
You might want to get more empty bottles before you go. If you don't have at least four of them, you will have to
leave the Pirate Fortress and go back in at least once. Four is the maximum number of bottles that you can get right now.
Here is how to get them (excluding the one that you already have from rescuing Koume in the swamp):
1. Defeat Goht to make it become springtime in the mountains, then win the race at the Goron Racetrack. You get a new bottle the first time you win. For more details, visit the After Goht page.
2. Before 2AM on the first day, buy a Powder Keg and take it to Milk Road (southwest of Clock Town). Use the keg on the big boulder and go into the ranch. At 2:30AM on the first day, help Romani prevent "them" from stealing the cows and she will give you a bottle. For more details, visit the After Goht page.
3. Do the Anju and Kafei Quest. Give Madame Aroma the Special Delivery in person to get the bottle.
Reach the Pirate Fortress
You can't get into the next dungeon until Lulu regains her voice, and she can't regain her voice until her eggs are in the Marine Research Laboratory. The Gerudo Pirates took the eggs, so their fortress is your next destination.
Remember to get the Stone Mask to make this next part easier. It's easy to get.
To reach the Pirate Fortress, go to the northeast part of the Great Bay Coast and go underwater. In the wall underwater, there are planks of wood with skulls and crossbones painted on them. Crash into the plank that is the second from the left. Go in to enter the Pirate Fortress.