After splashdown, the explosive hatch on Gus Grissom’s Mercury capsule blew off before the recovery helicopters could arrive, so the capsule got water-logged and sank.
Grissom was blamed though he claimed he did nothing; in support Scott Carpenter deliberately blew the hatch on his capsule after recovery, winding up with a big bruise on his hand - which the astronauts claimed was proof Gus had done nothing wrong.
It’s interesting that afterwards NASA quietly got rid of any explosive hatches on the Apollo capsules.
When the capsule was recovered 50 years later, it was proven that Gus didn’t do anything wrong.
Thanks. I was going off a vague memory from a movie and didn’t know the whole/real story.