yes , you can drive a car into the sea. it's easy, just rev up slap it in gear and let the clutch up. away you go. the faster you are travelling when you get to the edge of the water the further you'll get into the sea.
is in-your-ass how you like it? or should that be 'up'?
Keep an eye out for repeats of Top Gear, they did a channel crossing in a Toyota Land Cruiser (aka a Toyboater), but the Triumph Herald and the VW Campervan were less successful.