Induced Seaquake

You can deploy it only in your own watch, while the crossfire is empty, as you deploy a crew: never as a reaction, and not in the sortie phase. Once deployed, it waits in the crossfire like any card, and your opponent can react to it (802.10).

No target is chosen. As the card resolves, every crew in all berths is destroyed, yours as well: hull and plating don't matter. In your watch, that is every crew on board. It counts as being destroyed, so cards like Tunnel Rats are removed from the game. Bases and engines stay (801.9f).