cross fencing with backfencing is ideal... I don't know what water system you have, but you can use your reels and pegs to access it, just you need more of them. If the water is central, divide your paddock up around the water. If it's on a fence-line, run a lane to it using your polywire... it's a lot more work, but the difference between preventing backgrazing from 48 hrs and so resting the area for say 21 days rather than 14 really makes it worth it.
I've got a mob of calves in 3 ha now with a water trough on the fence line near the gate... they've got three reels in with them and really need at least one more so I can keep them on two-day sections. Remember all corners are weak points, if the voltage is good and they get through the polywire it's probably going to be at a 90 degree corner or where the wire crosses uneven ground and so is too low or too high. It only takes an extra peg to not make a 90 degree corner.