[School of Rational Thought]

Let me ask the obvious and tell me why this is not obvious.

The pirates hold a captive and therefore the US Navy hostage.

The pirates hold the hostage because they can physically control him.

So why not take that control away?

Why cannot a diver surreptiously sink that survival craft.

Pirates in the water is a more difficult scenario to control a captive.

Of course, the trick is to not have the captive harmed before they get in the water.

But once in the water, a diver can nab the hostage and provide air.

Once other pirates arrive, the game is over.

[A Navy Vet]

"Why cannot a diver surreptiously sink that survival craft."

My guess is that any noise coming from the hull would alert the pirates. The inside of an enclosed lifeboat is like an echo chamber.