Hi mark:
As Dr. Campbell pointed out, a lot of people make their own eardrops- usually with a combination of vinegar (acetic acid), alcohol, and/or water. Several alcohol based eardrop preparations are sold over-the-counter. I believe that most authorities feel that Otic Domeboro® (no alcohol) is the eardrop of choice to prevent inflammation of the external ear canal when diving, but it is only available by prescription. There is an over-the-counter eardrop called Star Otic® that is a close approximation of the Otic Domeboro® and I would think a fine substitute if you don't want to make your own or get a prescription. To really do their job, the eardrops should be left in each ear for 5 minutes.
Now, what eardrops do is help prevent inflammation of the ear canal from the water (and the gunk in the water.) When many divers complain of a feeling of fullness in their ears like there's persistent water in their ear canals after diving, what they're really experiencing are the effects of ear barotrauma. The barotrauma can cause injury to the eardrum, fluid in the middle ear, and/or swelling of the eustachian tube to the throat that can cause a feeling of fullness in the ear and decreased hearing. Eardrops won't help that problem at all. Prevention of barotrauma with frequent and gentle use of equalization techniques is the key to avoiding that particular kind of "waterlogged" feeling.
HTH,
Bill
[Edited by BillP on 12-14-2000 at 05:33 AM]