Welcome spring...and spring time allergies! While water in the ears can be a problem contributing to ear infections, most of the infections I've seen in 8 years of working for a vet have been the result of allergies, or occasionally resulting from antibiotics. Ear infections can be caused by both seasonal/environmental and food allergies and dogs can develop an allergy at any point in their life. At 2 years old, your dog is the prime age for developing/displaying environmental allergies. more frequent bathing (and especially ear cleaning) can actually be beneficial with environmental allergies because it physically removes allergens from the dog's skin. You could also try switching to a novel protein or grain free diet and see if that makes a difference. Some individual dogs are just more prone to ear infections regardless of what you do. Cleaning the ears at least once a week is crucial in breeds that are more prone to infections (such as labs, goldens, beagles, cockers, etc) to help reduce the number of infections and also to catch ear infections early.
You didn't say when you took your dog to the vet, or if you have been cleaning the ears. Most ear medications are twice daily and you really need to be cleaning the ears once daily while treating, otherwise all the debris from the infection will inhibit the medication's ability to do it's job. For the most part an OTC ear cleaning solution will work just fine. If the ear drum is ruptured you can also dilute betadine solution to a "weak tea" color with warm water and use that to flush/clean the ears once a day. The nice thing about betadine is that it will also kill yeast and bacteria so you are giving your ear meds an extra boost so to speak.
