What defense is there against something like this? AFAIK only a few US aircraft carriers are equipped with anti torpedo torpedoes, and one of those sitting in the straight would be pretty vulnerable.

Of course that could be the entire idea.

The calculation is that of course there are defences, but if you have a big stockpile of $20K drones, and your opponent has a limited number of $2mil drone interceptors, then you can keep throwing drones and keeping your opponent busy there, and you're coming out ahead even before one finally gets through.

See: https://bsky.app/profile/mekka.mekka-tech.com/post/3mgrvx5gr...