Flinging discs is by far my favorite activity. The magic of their flight through the air is enchanting. Let us not forget that there are fluids besides air.
Water comes to mind as a readily available, inexpensive, recreational fluid. Conventional frisbees cannot “fly” underwater. Too much viscous drag is my hand waving explanation. My question is what modifications to the air frisbee design might produce a practical underwater frisbee?
Drag is your problem, alright. I don’t see how you’re going to get around that. It takes energy to move that water, and it’s got to come from somewhere.
Better put a propeller and a motor on your Frisbee.
Drag is the problem, but the only way to reduce that (and still have a “frisbee”) would be to make the disc thinner, or something like an Aerobie. However, you still has to move your hand through the water to throw it, and that’s a lot of drag right there. You just can’t move your hand very fast, therefore you can’t throw the frisbee very fast/far. I’d think that you’d only get a maximum of a foot or two out of a frisbee thrown underwater. So keep your games close together.
No, drag isn’t the main problem. I’ve seen people on TV playing underwater-handball with a ball filled with saltwater. They were able to throw it a few meters and it sure looked like a nice game.
But you’ll more or less lose the gyroscopic stabilization. With the density of water, the slightest angle of attack is able to make a disc tumbling. Your stabilization has to come from the shape. There might be a compromise shape between high inertia, low area, and stability. I’m afraid it will look like a penguin.
And, people, always remember to avoid googling before posting.
Here’s the official aquadisc website: http://www.aquatoy.net/v5/products.html :smack:
Well, what do you know? I had no idea that would be possible.
They make “torpedoes” that you can throw back and forth underwater. They’re shaped like a skinny blimp with a pointy nose, and are heavy (the same density as water). You can throw one from one side of a back-yard pool to the other. I sure wish they had those when I was a kid! I’ve had great fun with them, and I’m 41 years old.
The air must really be thick where you live. 
toypedo: http://www.poolproductsdirect.com/toysandaccessories/toypedo.html Now that’s much more like the penguin shape I was thinking of.
“Being a fluid” or just “being fluid” means “being able to flow” (same root). It can be applied to gases as well as to liquids.