First off, this is not US Military, it is French (unless the us military changed languages) Secondly, that is not a bloody depth charge.
Considering they’re counting down and the size of the blast, i would say that was a French, small nuke test.
The french and US militaries are constantly working together to show how to use certain weapons they sell them. This was a demonstration for equipment (the depth charge) as well as a ship being sold to France by the US Military. The reason for the count down is pretty obvious, they know how fast it sinks, and what depth it will explode.
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