I have a technique I have developed over the last few years to test ice thickness with easy to find household items! First I throw the ball out and see if the dog comes back, if dog comes back 3-5 inches. Next I whip my sons x-box out there and see if son comes back, if son comes back 5-8 inches. Final test I toss my wife's Gucci bag way out there, if I make it back 7-10 inches.