Easiest way I can think of is two fast ships flanking the target ship behind, then moving forward in tandem, one on each side of the target, with a big cable or rope strung from one deck to the other. Just before they draw astern of the target, they move in closer to it from each side to put some slack in the rope, give it a bit of a U-shape and allowing it to drop into the water slightly and continue moving forward alongside the target till the partially-submerged rope contacts the prop, at which time the lines holding the rope to each ship are cut.
What I'm not sure of is if a tow rope can be affixed to the ship in such a way that the passengers or crew can't get at it to sever it. Ideally there'd be something under the waterline that frogmen could use to tie the tow-rope to, otherwise I'd just offer the tow and stand by till the passengers and crew accept it from sheer necessity.