I’m confused - if the sub was sinking anyway, why risk lives by salvaging 1/3 of the contraband? Surely the gov’t doesn’t need that much as evidence for a conviction, and it’s just going to be destroyed anyway. Grab a couple kilos and let the rest sink.
Well, typically yes, but everything goes better with coke.
I wonder if there are precedents for this? I know that the British navy actively pursued slave ships after slavery was prohibited in England (and before it was outlawed in the US).
Of course there are precedents. The precedent is that navies and coast guards can enforce the law of the sea even in international waters, and this has been the case for hundreds of years. Piracy is the most obvious example, but navies have been enforcing the rules since ancient times. Piracy, smuggling, illegal fishing, human trafficking (they used to call these slave ships), and on and on.
Most only did less than 10 miles per hour submerged, but close to 30 on the surface, which is why they stayed on the surface till they needed to dive. As for pretty quickly draining the batteries, I can’t really do more than guess, how fast they were going, or the electrical load a wartime sub would need.
Regarding your second question, a D/E is basically a mobile minefield. It has one shot, and then it becomes a datum point on a map. Unlike a nuke, it cannot get out of the AO quickly enough. If the story is true, and it was not just allowed to get through a battle groups defenses, then that Aussie sub taking a pic of the carrier, should give you an indication of how quiet these vessels are.