Minecraft Dungeons talk:Luck of the Sea

Luck of the sea is a new enchantment added in the free update for Hidden Depths on tier 1 it increases chance for rares to become uniques by 10%, tier 2 20% and tier 3 30%. It can be used on chests and merchants, including the Piglin Merchant. Tips: Get on all three enchantments for almost ensure every time you get a unique from a rare.
 * So this can be stacked?