Fronk is worried about his wife Mei, who went fishing in a floating place.
Quest Location
Talk to Fronk near the southwest entrance of Zora's Domain to start the quest.
How to Complete the Quest
You will find Mei on Wellspring island, at 3668, 0567, 1251, near a small rectangular pool of water. You can look for the smoke from her campfire to help find her. You can reach Wellspring Island by either going up the waterfall near Shatterback Point (south of Ihen-a Shrine) or by teleporting to Igoshon Shrine at the Water Temple and going southeast.
Talk to Mei when you find her, then go back to Zora's Domain and talk to Fronk.
Quest Reward
Mei gives you a Hearty Fish Skewer.