To do this you must first drive to the one of the random ramps that are off to the side of the road (that leads to the water and has no other side). Once reached drive to the end of the bridge in reverse(but very slowly) and fall. If done correctly then it will not say "totaled" or "you lose" and you can drive around .
Ok,you think looks are everything? Well, theres no problem with that, but put alot of mony under the hood BEFORE you trick it out,and you'll win races easyer for sure. Also, a better suspention is the best thing to put in first, so you can drop your car for more speed. Biger wheels (tires or rims) get you more distance to.