What Operation Crossroads showed about warships

What did the Operation Crossroads tests establish about ships and nuclear weapons?

They confirmed that nearby nuclear detonations, especially underwater explosions, were devastating to concentrated warships.

The tests were designed to observe how nuclear weapons affected groups of warships. Many targets were surplus or captured hulls left from the war, which made destructive experimentation politically and materially easier. The broad result was unsurprising but important: underwater nuclear blasts were especially damaging, and close surface or air bursts were also catastrophic. The passage is a concise entry point into why fleet dispersal and nuclear survivability became Cold War concerns.