Act II - Nautica, turtle in the house above the Weapons shop
Secrets of the Sunken Spirit
Once you've defeated Alizarin, return to Nautica and speak to the Queen to become a fish. Swim above the weapons shop to find this turtle looking for a special item to display in his museum. Zoom over to Lonalulu and head to the Canon Lady's house north of the Item shop, she'll give you the Kanono Canon upon speaking to her. Return to the turtle and deliver the item to complete the quest.