Having just got over 6 weeks off diving and 5 visits to the ENT specialist. I know more about swimmers ear than I used too. Now I use the commercial Swim Ear stuff because it doesnt dry the ear out which can lead to aural dermatitis, it provides a light oily film which protects the ear canal. Bacterial infection is caused by the ear way getting sodden every day and infection setting in. Worse in warm fresh water. The vital takeaway from the ENT doctor was not on any account to use antibiotics. This kills off bacteria in the ear which invites a potentially worse and hearing damaging fungal infection.