Wait, since it's an abyssal MINE, it shouldn't explode by hitting it like that ?
Depending on the stability of the explosive, and the method of detonation, it's possible. Generally speaking, beating explosives that have no detonator at all is a really, really bad idea in and of itself, anyway. But regardless, naval mines were typically magnetically triggered, so as not to blow up every time a fish or driftwood bumped into one. Presuming shipgirl bodies aren't made of metal, and she's not wearing her rigging, the detonator wouldn't be a problem.
