Water polo ball

A water polo ball is a ball used in water polo and canoe polo, usually characterized by a bright yellow color and ease of grip ability, so as to allow it to be held with one hand despite its large size. 
Standard water polo ball characteristics.
Ball weight is 400-450 grams (14-16 ounces) and inflated to 90-97 kPa (kilopascals) gauge pressure (13-14 psi) for men and 83-90 kPa (12-13 psi) for women. Water polo balls come in two main sizes: a size 5 (68-71 cm in circumference), intended for use by men, and a size 4 (65-67 cm in circumference), intended for women. Smaller balls are sometimes used by juniors for "mini-polo," though these miniature balls do not typically come in standard sizes and are often coloured green.
Development of the water polo ball.
The modern game originated in the late 19th century as a form of rugby football, played in rivers in England and Scotland, with a small 3 to 4 inch ball constructed of rubber imported from colonial plantations in India. This "water rugby" came to be called "water polo" based on the English pronunciation of the Balti word for ball, "pulu". The original ball soon gave way to a football (soccer ball), which allowed for passing and swimming above water with the ball. However, the leather football absorbed water and became extremely heavy, slippery and out-of-control when wet. In 1936, James R. ("Jimmy") Smith, California water polo coach and author of several books on water polo mechanics, developed a ball made with an inflatable bladder and a rubber fabric cover, which improved performance. The new ball was red, but by 1948 yellow was adopted for better visibility by players. It became the official FINA and Olympic ball in 1956.
Recent changes to water polo balls.
In the first half of 2005, FINA allowed a change to the standard water polo ball used in official games. This change permitted a coloured middle stripe (blue, green, red, black, or yellow) with the normal yellow stripes flanking the coloured.
In May 2006, the NCAA and National Federation of State High School Associations Rules Committees announced a rule change allowing the colored balls to be used in all NCAA and NFHS sanctioned games. The current rule states that the water polo ball must be “yellow with black lines,” but new wording will allow for colored panels. Mikasa Sports, manufacturer of the new colored ball, claims that the new ball benefits teams by making it easier for them to keep track of their balls, differentiating the women’s balls from the men’s and teaching proper rotation on the ball.
Unique designs and color combinations have been used to commemorate special competitions.