An atomic bomb blast in San Diego Bay? No. More like a mushroom of smoke, mud, and water propelled by 2,040 pounds of TNT in seven feet of water. This bomb was detonated by the Naval Electronics Laboratory just a few miles from the Hotel del Coronado in June 1946. The scale model experiment recorded wave intensity from underwater explosions. The San Diego blast was a warm-up exercise for the world’s first underwater nuclear bomb explosion at Bikini Atoll in the Marshall Islands on July 24, 1946.