The RN weren't sure before the first Swordfish attack whether they had spotted the Bismarck or the shallower draught Prinz Eugen. So they set the torpedoes to a compromise run depth before launching. This is why the torp hit the Bismarck's armour belt rather than below it.
The second attack was flown in a force 9 gale. The Ark Royal's deck was taking water forward and the stern was rising and falling 60-70 feet. No other carrier aircraft of the time would have been able to get off the deck, let alone launch an attack. All but one Swordfish made a safe landing.
The hit on the Bismarck's rudder jammed it and it was this that let the rest of the fleet catch up and sink it. At Taranto the RN used duplex fused torpedoes. These could either explode on contact or below the hull with a magnetic fuse. Some of these put 30 foot holes in the bottom of the Italian battleships.
Having said all that it would be a bit pointless to intoduce the Swordfish to AH. It would be cannon fodder in the MA, even in EW, and there's not really any scenarios it would be any good for either. The only big action it fought against aerial opposition was the Channel dash, where six Swordfish went up against 40 ships and around 60 LW fighters.
If you want a good RN attack plane, go for the Fairey Firefly. Four Hispanoes and Fowler flaps, it could outturn a Zero.
