Lake Jarrah is a location found in Breath of the Wild.
The Lake is located just south of the Equestrian Riding Course and west of the Midla Woods. Water from Lake Jarrah flows westward into the Fir River, which continues onward to the Squabble River, Hyrule River, and eventually into Lake Hylia. Due to the Lake's proximity right next to the riding course, there are numerous dangerous enemies, including Moblins. However, There are also a number of Water Octoroks that can be found throughout the Lake. A Raft located near the north end of the Lake that can be used to navigate the water.
There are several treasure chests to be found throughout the Lake. Right in the center of the lake there is a treasure chest that contains five Shock Arrows. At the east end of the lake there is a wooden chest that is floating around that contains a Purple Rupee. At the north end of the Lake, near the ruins in the shallow water, there is a treasure chest that contains an Opal. Right on the land at the southwest part of the Lake, there is a treasure chest that can be pulled out of the ground using Magnesis and it contains an Amber gem.
In the small batch of land, just southeast of the Lake, there is a rock that when lifted, will reveal a Korok.
Nearby Korok Seeds
Seed is on top of a small hill. Use Magnesis to move the door and then pick up the boulder underneath.
The rock. Pick it up.
This one takes a bit more work than usual. The nearby dirt road makes a loop which has 10 signs on it with bullseye targets. Shoot to destroy them all. Once you have, a balloon appears over the nearby cabin. Shoot it too for the seed. The cabin contains a chest with 10 arrows, if you're in need.