Here is another suggestion one of our parent's doctor recommended:

Using a blow dryer on a low cool setting to completely dry the ear. On this other swimmer's case which is a little more complicated the doctor has advised not to instill any drops in her ears. May be just in her case, but the blow drying thing has helped (along with antibiotics!).

Parents  you can also use ear plugs to prevent the water from getting in the ear as well. There are over the counter ones but this mom found some from an ENT doctor on Huebner road. They come in several sizes and are fitted to the child's ear.
 

Thanks,

Coach Claudia