From Dragon Mania Legends Wiki
Introduced in Update 3.7, the Whale-Mart is a floating market located south of the Main Island where Trainers can exchange different resources for other kinds of resources. The Whale-Mart is run by Mishiyo and is only visible between Friday 12:00 UTC and Sunday 12:00 UTC. The time remaining until the Whale-Mart departs is shown inside the bar.
Accessing the Whale-Mart will bring up the five available offers, the time remaining until the whale departs, and a random message from the merchant. Outside the Whale-Mart, the icon is shown atop it, regardless if there are any available offers in stock or not. The Whale-Mart is unlocked at Level 5.
While some Trainers may receive the same offers, the offers generally vary by groups of Trainers or by Trainer level. All offers have a limited inventory of stocked goods. Depending on the offers, the Trainer is usually able to trade Gems, Scrolls, Portal Gems or Food in exchange for Enchantment Materials, Portal Gems, Dragon Pieces, Dragon Fury Essence, Food, decorations, Habitats, Relics, various tickets, or Habitat Limit Extenders.