[Sailor Steve]

I think it's "Block & Tackle", and yes it should take an hour or so. The "external" storage is a storage box under the deck. They have to set up the little crane, winch the 1-ton torpedo out of the storage, open the torpedo loading hatch, winch the torpedo down the tube, close the hatch and put everything away.

You can't dive with the torpedo hatch open. If you close it and dive you'll lose the torpedo, and maybe the crane too. In any case your dive time will be longer because the on-deck crew have to get below. If the torpedo is in the tube and you can't close the hatch you're stuck.