The Byroad to Lanayru Wetlands is east of Sahasra Slope and can be entered at the north edge of Lake Siela.
Cave Location
The Byroad to Lanayru Wetlands is located at 1613, -1257, 0008. The entrance is east of Sahasra Slope Skyview Tower, at the north side of Lake Siela. There is another entrance at 1609, -0806, 0009, at the west side of Telta Lake, north of Kakariko Village.
Cave Features
To enter the cave, you need to either swim or use a raft. On the left, there are four Horriblins. A Big Hearty Truffle can be found on this side of the cave. On the opposite bank, there is a Shock Like. A rare ore deposit can be found on this side. There are also wooden planks here that you can use to make a raft if you have a fan and steering stick.
Farther in the cave, if you go to the left, you find a Stone Talus (Luminous). If you go to the right, there is a wooden chest in the water that contains arrows. Farther ahead, you will see the cave's Bubbulfrog on the wall.
Beyond that, the cave opens to the outside.