Ploymus Mountain and the Lynelīefore leaving the domain, talk to Laflat, a Zora that will give you a side quest that involves taking a picture of a creature called the Lynel. This head gear increases your swimming speed, as well as giving you a spin attack while swimming underwater. Reel the chest up and you will get the Zora Helm. You will find a submerged ruins in the area, so look around using your Magnesis Rune until you spot a chest under the ruins. Head north of the domain and use your Zora Armor to swim up the large waterfall and go up to the very top to reach Toto Lake.
Before heading to the east waterfall, there is an inscription around the area about the Zora Helm.
