It would be awesome, if a car or plane falls in water, to have a giant splash of particles (like the tank gif you sent)

This wouldn't work well with a good number of packs, mainly due to the fact they don't have collision boxes except on the hood, trunk, and roof. Would make for a rather funny particle effect. While it does sound like a good idea, it's not really feasible given the collision box restrictions imposed by MC's block-based layout.