Hi Liliput, I have extensive experience in using fillers for the cheek, the chin, and lips. To be honest, none of my patients ever brought this issue up. Underwater pressure won’t displace the facial filler because it isn’t hollow, but according to DAN or the Divers Alert Network, the physical pressure from the mask strap alone (kept very snug to keep it from falling off) is enough to displace the fillers. Making sure that the pressure is equal between your face and the mask is difficult if you are feeling any kind of discomfort. Your doctor can assess if the fillers had settled with little chance for displacement. Typically, this should take around two weeks, barring any complications. Some people have adverse reactions to fillers so if you experience symptoms like inflammation, pain, difficulty swallowing, or nodularity, then you need to see your doctor - even before you plan a trip. I hope this helps. All the best, Justin Harper, MD.