if im not mistaken, is this the boat racing? (sorry haven't played vc for a looong time)
if it is, here are my tips:
1. Don't rely on Lance so that he can blow up other boats. Most NPCs have bad accuracy 2. If you are at a narrow area, release the gas(meaning you release W/X/whatever platform you use) 3. Don't try to shoot them using your submachine gun as it won't be very effective.
I had a bit of trouble with this mission also when they go right through the narrow canal go to the left youll then see a narrow strip of the golf course that it looks like you can jump DONT TRY AND JUMP IT instead turn right then left and you shouldnt be to far away from the yacht.