Can wheeled vehicle run on the surface of water at high speed?

If it worked... top gear would have done it in the Clarkson Hammond and May years. Those guys inadvertently proved with unlimited budget and a bit of no how it's still hard to beat established products.

 

That top gear was very heavy. Something light as a human powered floating hamster wheel is more in line with my thinking, however let some military with a large budget do the research and find out.

The Porcshe would make a nice boat inverted. Better than this:

Dutch Artist Recycles Car As A Rowing Boat Photos and Premium High Res Pictures - Getty Images https://www.gettyimages.co.uk/photos/dutch-artist-recycles-car-as-a-rowing-boat

 

I was of course kidding about the Porsche body. While it might look cool, I doubt it would be a good shape in the water. For starters, it's way too fat for the water, which has more viscosity, and sports cars moving on the land don't need to worry about the same types of bow and stern wave drag, because they aren't really creating gravity wave wakes. For that matter, fast cars try to increase the friction of the tires by using a shape that produces a strong downwards force, whereas very fast boats plane, to reduce the downwards force. Also, air is a compressible fluid, whereas water isn't very compressible. Also, the speeds at which turbulence creates a lot of extra drag are somewhat different.

Sports and race cars also try to achieve very controlled steering (one of the reasons for desiring a strong downwards force). They need good steering to go around corners fast, and because race cars typically jostle and smash each other out of line during races. But motor boats mostly try to slide through the more viscous water with minimum resistance, which means they have much less control. And for the most part, you don't want to jostle and smash into other boats. (There are some insanely dangerous types of boat racing where they do push each other out of the way - but I assume that isn't the o.p.'s goal - that he is a solo boater, who just wants to enjoy being on the water.) Kayakers and canoeists, steering around rocks (and gates in slalom racing), or navigating through currents, do sometimes achieve something close to controlled steering - but they take advantage of strongly edging the boat , and/or placing and/or moving the paddle at a position offset from the boat (sort of like a sailboat offset board or leeboard?? - I don't sail) - which maybe isn't very good streamlining for a motorboat going fast in flatwater or open water (which I assume is what you have anywhere you have crocodiles), so an efficient fast boat wouldn't try to achieve the extremely high precision steering of a sports or race car. It's a different domain, and precision steering isn't as important.

Sports and race cars also need to accelerate fast (another reason for wanting a strong downwards force to increasing tire friction, rather than decreasing drag). There is little reason for a solo recreational motor boat that isn't racing to accelerate fast, outside of whitewater and surf boating. (Maybe smugglers sometimes need to accelerate fast, but that's a special case, which I assume the o.p. isn't after.)

Another thing. A boat that is efficient at low speeds isn't efficient at high speeds. So, it doesn't make sense to shape your boat like a speedboat, if you are going to go 4 knots. The speedboat planes - i.e., it pushes water downwards to lift the boat somewhat out of the water, because water has much more resistance than air. But at low speeds relative to the water, planing is mostly a waste of energy. Again, a displacement (non-planing) boat that wants to go fairly fast needs to have a high length/width ratio, so you don't waste too much energy pushing water out of the way, but at slower speeds, the ratio should be less, so you don't have too much frictional force against the sides and bottom of the boat. And, BTW, a high length/width ratio makes it harder to achieve precision steering.

Stability is a bit different too for low and high speeds. At low speeds you are mostly concerned about not rolling over. At high speeds, you also need to worry about somersaulting end over end.

Anyway, you should decide how fast you will ultimately want your boat to go, and shape it accordingly. And you should give up on high precision steering, unless you have a very good reason for it, because it will interfere with straight line efficiency.

The examples you have posted don't give a very consistent picture of what you want your boat to do. In general you may want to decide how you are going to use your boat, and design it accordingly. Do you just like being out on the water? Do you want some sort of sun shade? Do you want to fish? Do you want to play with the waves and currents? Do you want to go fast? Do you want to go on extended multi-day trips? Do you sometimes want to carry other people? Do you want to show off and attract mates? Is there a lot of seaweed or algae to deal with? How deep is the water where you want to go? Each of these goals would change the optimal design. There are other people here, with an engineering background, who could do a much better job of explaining what type of boat would best meet those goals than me, but first you have to decide what you want to do. Even within the limits of something that fits in or on your car, you should try to give more specifics.

In addition, if you can afford a Porsche, maybe you can find something off-the-shelf that will do what you want, rather than building your own. E.g., there are "amphibious vehicles", that have been discussed in other threads, that could drive on the road, then go directly into the water. Then you don't need to fit your boat into or onto your vehicle, or spend time putting it together. Unfortunately, when I looked them up, they were all astonishingly expensive by my standards. (At the lower cost end, some people who just want to cross slow moving streams take 4WD trucks, possibly add a bit of flotation, add a "snorkle kit", so their air intakes and maybe exhausts are above the water, and drive them into water. But the rust and maintenance problems must be horrendous, especially in salt water, because that isn't what land vehicles are designed to do. And AFAIK, none of them go fast in the water - in fact they could be carried away by even mild currents, though you maybe could add an outboard motor, or strap something to the wheels that would let them move water more efficiently.)

 

That top gear was very heavy. Something light as a human powered floating hamster wheel is more in line with my thinking, however let some military with a large budget do the research and find out.

The Porcshe would make a nice boat inverted. Better than this:

Dutch Artist Recycles Car As A Rowing Boat Photos and Premium High Res Pictures - Getty Images https://www.gettyimages.co.uk/photos/dutch-artist-recycles-car-as-a-rowing-boat

 

After a 20 minute speedboat ride at 30 knots over open seas I can say that the ocean does feel somewhat solid underneath, enough to support some weight, at speed this is not water but rough mushy terrain that needs a properly suspended dune buggy to ride over. If power requirements are less than for a similar capacity boat, then it will work.