I have never caught a shark (or even fished for one) but I have caught lots of other interesting fish off the back of my boat.
Sailing back from Hawaii to the PNW we caught several Mahi Mahi. We were using big plugs on parachute cord with a bungy loop to the boat. When the fish hit it the bungy would snap tight and set the hook. We then just hauled the fish in. We caught them at speeds up to 10 knots (the fastest the boat would go). We also caught a couple small tuna that trip once we got farther north. Same rig and boat speed.
Last summer we caught loads of salmon. We used a rod and a diver to get the flasher and hoochie down deep. The boat was going very slowly, about 1.5 knots) and we had great luck. We have caught Coho going faster but not as many. We use a bucktail and tow it in the wake of the boat so it just jumps out of the water every once in a while. If there are Coho around it is a killer setup. We don't have refrigeration so we throw the big ones back and only keep what we can eat in a single day.
Great way to have fresh meat.
One word of caution. Here i the north you have to be careful where you clean the fish. If you get fish guts and blood on your boat or dinghy you are inviting bear trouble. Although it has not happened to us, we have heard of folks who left their dinghy on the beach and came back to find it shredded because it smelled of salmon.
There is a tide in the affairs of men,
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
Shakespeare, Julius Caesar IV, iii, 217