Swimmer's ear should go away within a week or ten days if treated using prescription ear drops for the swimmer's ear.
As another alternative you can use Rubbing Alcohol and Vinegar to make ear drops to get rid of swimmer's ear.
Just mix half Vinegar and half Rubbing Alcohol in something and then use an ear dropper to drop a few drops in your ears.
The rubbing alcohol will evaporate the water from your ear.
You can also lay on your side and allow gravity to force the water out of your ear.
Treatment needs to be done as soon as possible for swimmer's ear because if swimmer's ear is left untreated you risk losing your hearing.