Could chemicals reacting with seawater explain Kongō's explosion?

Could chemicals reacting with seawater explain Kongō's explosion?

Such materials should be kept from contact with seawater. Chemicals sealed inside an intact shell would not be exposed simply because the ship flooded.

Ships use seawater for firefighting, so materials that react violently with it should be kept from exposure. A reactive ingredient inside a shell's explosive filling would normally remain enclosed. Floodwater would need a way into the shell before that ingredient could react with it. This objection challenges the proposed mechanism without identifying the actual cause of Kongō's explosion.