Our earplug simply keeps water from coming in contact with the ear canal and eardrum; it does not keep the water and pressure out of the ear canal. The ear canal and eardrum are at the same pressure as the external water pressure plus the pressure needed to dilate the diaphragm, virtually the same as if you were not wearing any ear protection and far less than a conventional swimmers earplug used 1' below the waters surface.
There are presently no earplugs made for swimming that will not cause damage to the eardrum when used below the surface of the water. How deep before damage occurs is a matter for conjecture, individuals with ear problems are going to be affected before those without ear problems but damage will occur well before the 10’ level that many swimmers earplugs advertise as the safe depth for use.
Conventional earplugs seal off the water pressure from the ear canal on the exterior and the tympanic membrane (eardrum) seals off the canal from the interior creating a trapped dead space where pressure cannot be equalized without rupturing the tympanic membrane. Some brands of regular swimmers plugs, claim their safe, to a depth of 10' (4.5psia trapped) at 5' there is 2.25psia trapped between the plug and eardrum, at 1' there is .445psia trapped. Our earplugs (Patented as Ear Prophylactics 7,185,655) begin working immediately upon leaving the surface and there is less pressure on the eardrum at 100’ than with a conventional swimmers earplug at 2’ or 3’