Water skis are used for
water skiing, a very fun summer water sport. No, you don't need two skis to water ski, many people do just fine with only one. You can even water ski
barefoot, but that takes some
talent and a very fast
speed boat.
You should always wear a life jacket when you are water skiing, because there is a chance you could be knocked unconcious and drown, which would bum out all your friends.
To water ski, sit in the water with skis strapped to your feet wearing your life jacket, and grab on to a tow rope attached to a friends speed boat. As the boat pulls your body forward, lean back and relax your knees, and you will be lifted out of the water and up onto the wake. Then you just ride around until you eventually become to tired to stand up anymore and crash back into the water.
When climbing back into the boat, watch out for the dangerous propeller, the spinning blades at the rear of the boat. You don't want to lose a toe!