Camellias are no different from most ornamental shrubs. They have to have water to survive. Not enough and they can perform poorly or die, and too much they can perform poorly and die. Balancing their water requirement is not difficult to do.
Camellias like to be moist, not wet. They like to be well drained. They do not do well with excessively wet or dry roots. We use overhead irrigation at our nursery for our camellias and on some things we use drip irrigation. The best looking ones where we have used overhead irrigation and not only irrigates the roots but keeps the foliage looking nice as well. Just dont’ water late in the day if you can help it in climates that are moderate and warm or you could have funal issues.