salvage

Objects.

Specifically maritime or marine salvage, I would think.

But the police? I've read about people in cars under water. These are also salvage operations.

Webster's defines salvage as:

1 a : compensation paid for saving a ship or its cargo from the perils of the sea or for the lives and property rescued in a wreck b : the act of saving or rescuing a ship or its cargo c : the act of saving or rescuing property in danger (as from fire)
2 a : property saved from destruction in a calamity (as a wreck or fire) b : something extracted (as from rubbish) as valuable or useful

In this case, it sounds like definition 2a or b is the applicable one. Note that salvage generally refers to property.

People in cars underwater involve either rescue operations (if they're alive) or are forensic in nature, i.e., looking for evidence of crime or cause of death (if they're dead). In the process of doing one or the other, the car would be salvaged and the people rescued or the bodies recovered.