Want to break the world record:

Jerdone Coleman McGhee of Wimberley, Texas, holds the current Guinness Book of World Records title for a 1992 toss that yielded an impressive 38 bounces across the Blanco River in central Texas.

Then here is what you need to do: toss the stone at greater then 25 miles per hour with a spin of 14 rotations a second and assure that it enters the water at an angle of 20 degrees.
The article does not talk about the impact of wind and water conditions.