Pond Island

The Pond Island item creates an Island covered with Sand, water, Prismarine, Prismarine Bricks, and Dark Prismarine with stone underneath. It also contains a Fishing Crystal, which grants a chance of fishing Prismarine Shards and Prismarine Crystals in nearby water, with an effective diameter of 15. The pond island has water in it.

Crafting
It can be crafted when you reach Raw Fish IV.
 * 3x 5 Sand
 * 3x 5 Prismarine
 * 3x Water Bucket