USWP is pushing a very good video by Fargo on individual ball handling skills that I feel is excellent. The key is motivating your players to spend the time working with a ball in the water and on land until they can really handle a ball. I can remember watching John Vargas sit in front of the TV playing with a water polo ball by the hour. He was absolutely excellent at spinning the ball and doing all kinds of tricks with it, He could get it spinning and put it on his dark glasses and it would spin on the frame. He would also spend hours kicking the ball from his foot to his knee to his head back to his knee etc. He could roll the ball up his shin and back to his foot. There are so many things a player can do with the ball while laying on his back in the water and using both feet, knees, hands, and head that I don't have the time or space to deal with them all. But all of these teach ball handling and body control in the water which will go a long way in developing ball skills and body control.
Some of the simple ones that Fargo goes over players like John Vargas have been doing for year. John was good at them when he came to UCI in 79. So I am sure he figured them out or got them from his brothers Joe and Chris when he was just beginning playing in his back yard pool.
I will go over a few simple ones and then it is up to you as a player or coach to think about these and add new ones that you think up.
Start off with getting a smooth ball not a new one. Handling a slippery ball really helps you develop better skills. Most of us have plenty of old smoothies. For some reason we have always called these balls razor blade balls. Shaven smooth. Start by keeping the arms straight and tap the ball back and forth between your finger tip while moving your arms up and down. You can also do the same movement moving right or left in a circle. . This gives the player more leg work.
Next take the ball and squeeze it off your finger tips going from hand to hand or off one hand several times and then shifting it to the other hand. This can also be done moving right or left. Put both arms out straight off the shoulders and pass the ball over your head; at first do it watching the ball but try to work up to passing it while looking straight forward. Then throw the ball up and over with either the right or left arm and spin or draw 180 degrees and catch it with the same arm. Then throw it up and spin or draw 360 degrees and catch it with the opposite arm. If you get good go for 720 degrees. Start the ball on the back of the hand and flip the ball up to the palm of the hand working both the right and the left hand. Then when you get the ball up over your head try to spin the hand around the ball going both right and left.
As you improve you can spin it around many time both directions then go back to the back of the hand to the palm. Get the ball spinning on a finger and draw 360 degrees and keep it spinning transfer it to the other hand and draw around the other way. Get the ball spinning on a finger and then run the ball across your arm and chest to the other hand and throw it back to the hand you start with. Try doing it with both the right and left arm. Next get it spinning and have it run down your arm and across your neck and to the other arm and then back. If you are innovative you can think of all kinds of ways to spin and move the ball around on your body. Doing this in the water also really works the legs. Balance the ball on the bridge of your nose. Great for body balance in the water. Bounce the ball off your head you can get pretty innovative on this by bouncing and spinning the body around or get a partner and bounce it back and forth.
Last take the ball around behind you with your right hand and arm and grab it with the left hand and push it to the right arm and do it again then go the other way great leg drill and ball handling drill all in one. These are just some of the things we do. If you are innovative you can think of many different individual skills that are fun to do that will help your ball-handling skill.
Next as I tell my players over and over again you can never practice enough on your catching and passing skills. It is key when you pass that one learns to catch and pass in as many body positions as possible. I get many high school players coming to UCI who always want to catch, pass and shot with their hips up on their side. Therefore in a game if the defense knocks their hips down they can't pass or shoot. That makes playing the game rather difficult.
The more you the coach can motivate your players to work on their individual ball handling skill and get them to pass and work on their passing , catching and shooting skill the better your team will perform. There are no secrets. Secrets are for losers, winners know it all comes from time spent working and developing the basic skills. If you have the skill then you can learn and play any system that will be needed to perform against your opposition.