One of the most important physical attributes for any successful diver is upper body strength. The ability to "throw" a dive and perhaps even more importantly, the ability to "hold an entry" (aka RIP a dive) especially when hitting the water at 35 miles per hour!!
One easy way to work on upper body strength with your divers on an almost daily basis is to have them CLIMB OUT OF THE POOL AFTER EACH DIVE. DO NOT LET THEM USE THE LADDER!! If your diver does 50 -75 dives per practice, this amounts to 50-75 "dips" or push-ups that they do at every practice and over time this does wonders for the biceps, wrists, tri-ceps, lats and shoulders.
It may be difficult at first -- but in the long run, it will make a big difference!