A jewel thief hides a diamond by placing it on the bottom of a public swimming pool.

A jewel thief hides a diamond by placing it on the bottom of a public swimming pool. He places a circular raft on the surface of the water directly above and centered over the diamond, as shown in the figure below. If the surface of the water is calm and the pool is h = 1.52 m deep, find the minimum diameter of the raft that would prevent the diamond from being seen.