# Can it run on water?

Some months ago I made this thing, it doesn't have a name.So let's just call it Jonathan like my brother.

Basically a lizard in erect posture with the head of a mammal, two ''tentacle'' antennas in the head,five talons, 3 fingers and 1 thumb for each respective limb. Given a weight of 70-80 kilograms most of it being muscles or bone with a body fat almost absent, most of the energy is stored in two sacks along the neck. and a height of 165-175 centimeters, can Jonathan run on water like the Jesus lizard ?

If it's not feasible, what non-drastic changes on Jonathan's physique could help?

• By referring to mass casually as weight you are implying Earth gravity. But maybe he lives on a planet with different gravity as that can make a difference? Jul 27, 2016 at 14:54
• The posture you show is not in balance. He needs to be leaning forward to keep the center of mass over his legs. Jul 27, 2016 at 14:55
• @jdl he's using his tail as a part of his support. Kangaroos do the same, iirc Jul 28, 2016 at 13:21

No, it can't.

There is a species of lizard which manages to walk on water because it has wide "foot-print" which acts on the surface tension, and thus allows it to float - albeit temporarily.

This creature places its weight in two fairly focused points which end in claws. That will work about as well as you might imagine.

Of course, if it were to run at idk how many hundreds of kilometers per hour it might "skim" across the surface, but basically everything will, at that point.

• No. The basilisk lizard's feet don't act on surface tension, and the velocity that a human sized creature would need to run on water is answered herein, and it isn't many hundreds of kph, it is between 50 and 100 kph. Jul 27, 2016 at 21:37
• @JamesK for a human sized being, to run on water, at any speed, would be near impossible. Each step you are placing your entire mass on the water, the being would instantly sink. It may, if going fast enough, start to sink, then skim/ skip across (and unnaturally.) Jul 27, 2016 at 23:50
• @EvanCarslake actually, all you have to do is rely on the inertia of the water. Water does not instantly move out of your way, as any poor high-diver who has mistimed their dive knows far too well. You can use this to run on water. All you need to do is apply a force on the water equal to the force of gravity on you. This will accelerate the water rather quickly, but not instantly. The actual accelerations would depend on the mass of water that you're moving. Jul 28, 2016 at 2:12

Simply put...no it can't.

For something of humanoid size to run on water its feet would have to be HUGE and they would have to move incredibly quickly which would require more muscle mass which would in turn require even larger feet which would require more muscle which...well I think you see the point.

The most well known (to me) creature that runs on water is the Basilisk Lizard

This guy uses his light weight, large fast feet, and foot flaps that produce air bubbles to run on water.

The dimensions/weight of the lizard should give you an idea of how ridiculous a humanoid would have to look for this to work...

If my off-the-top-of-my-head math is correct, we would have to have feet at least as large as say tennis racquets and they would have to move at near 65 mph.

Changes to make it work

You could do some things to make this easier to believe, for example make them somewhat smaller, perhaps with lighter weight bones.

Being from a lower gravity planet...or if you want it to work on Earth perhaps from a higher gravity planet and then all of a sudden their strength and wide base allow them to run on water...there are options but what you decide needs to have the right balance of Foot size, speed and total weight

• "If my math of the top math" ... huh ? That sounds weird :) Jul 27, 2016 at 14:58
• @KingofSnakes Thanks! Apparently I went brain dead there for a second. Jul 27, 2016 at 15:12

Maybe Yes

Man running on water has been the subject of several scientific papers. In particular Google for papers by J. W. Glasheen and T. A. McMahon. They studied the basilisk lizard, but their results can be extrapolated to humans. It's debatable how reliable such a large extrapolation is, but the result is that the required speed is so far beyond human ability that we can safely conclude it's impossible without some artificial aid.

There's a summary of the results from the papers in this article and a more general summary here. The conclusions are that you have to run at a speed of 30m/sec, almost 3 times as fast as Usain Blot (10.4 m/sec). Which doesn't sound too bad, but you'd need to generate a mechanical power of 12kW to do it. Trained athletes can just about manage half a kW, and most of us would struggle to generate 200W. If you generate 12kW, you would probably be roasted from within.

You can reduce this by having wider feet, webbed feet, stronger muscles, some way to dissipating heat, the most ideal way would be to reduce its height and weight. Even then it would hard for a being to keep it up for a more than a few seconds time.

• Follow up article: It can be done in reduced gravity. journals.plos.org/plosone/article?id=10.1371/… Jul 27, 2016 at 14:23
• What about some sort of foot design that traps air under the feet (between the feet and water)? It might not be able to stand or walk slowly on the surface, but if its toes were longer, spread further apart, and webbed, and shaped in such a way that they could trap air pockets momentarily, wouldn't that aid buoyancy for running? Perhaps it could even walk flat-footed on land (for better balance/grip), but "cup" its feet when running across water to trap the air? Jul 27, 2016 at 16:56

No, it can't

As several other people have mentioned, the feet on this animal are too small to generate the sort of buoyant force needed to run on water. However, there's another problem that this creature will face: its legs look too weak to generate anywhere near enough force.

Your creature already has fairly weak-looking legs compared to someone like Usain Bolt, the fastest human runner. However, it also has a gigantic tail that looks like it would weigh almost as much as its body. The more extra weight a creature has to carry, and the more of its body weight is carried in anything but leg muscle, the harder it's going to be for the creature to run across water. Your creature also appears to have no gluteus maximus muscles, so as depicted running much at all is going to be difficult.

What changes do you need to make?

• Give it gigantic leg muscles.

Think several times the size of human leg muscles. This creature needs to be an incredibly powerful sprinter if it's going to run across water.

• Make the tail smaller.

Right now, your creature has an enormous, thick tail. If you want it to remain tailed, make the tail significantly thinner. This will reduce its overall body weight. For a tailed creature, you should also change its posture so that its back is horizontal to the ground. Less "person" and more "velociraptor".

• Make the feet bigger, with longer toes.

Surface area is a good thing! If you want your creature to be able to run on water, give it bigger feet to help it do so.

• Make it smaller.

Remember the square-cube law! Basilisk lizards can run across water despite having tiny, skinny legs because they're small. Their legs are proportionately far stronger than human legs, and the viscosity of water is the same regardless of how much you weigh.

Add some vestigial wings which catch the air during forward motion and lift enough of the lizard's weight to allow the rest to skim across the surface on the width of its feet alone.

Sort of like the overweight duck in the pond behind my house.

Archimedes' principle: A body displaces a volume of water equal to its mass.

To WALK on water, I'm assuming, only its feet and tail should be in contact with water. These, mostly the feet, should have a volume of 70–80 litres in total.

• I'm not a physicist, but surely this doesn't apply when there is propulsion involved? An object that would normally sink based purely on its density can use energy to keep itself above the surface.
– user16107
Jul 27, 2016 at 15:18
• According to you ideas things heavier than air can't fly. Jul 27, 2016 at 16:36
• The question specifically mentions, what non-drastic changes on Jonathan's physique could help? Heavier than air objects require two things: a) sufficient speed and b) aerofoils (wings) of sufficient area. The combination of the two generates lift to counteract the objects weight in a fluid. The amount of a) required depends on the size of b). In any case, given that any amount of wingspan, that might make running to generate sufficient lift feasible, is, to my mind, a "drastic change", mentioning it is redundant. Also, I stressed WALK. Jul 27, 2016 at 16:48