The peroxide is a good idea. If it doesn't work, then try vinegar.
Also, have you tried sleeping on that side of your head? Gravity can help your ears drain.
Or, you can tilt your head to that side, but instead of banging, try pushing and pulling your finger out of your ear really fast. It'll be uncomfortable, but it makes some good suction to get the water out.
My swimming coach used to have us do this stuff all the time, and it helped with water in the ear alot.
But you should try the peroxide/vinegar first, because if there's earwax somewhere holding in the water, then that will have to be removed.
Good luck!