How can I keep my ears from popping underwater?
Just use the Valsalva maneuver is where a person tries to exhale forcibly with a closed glottis so no air exits. Works great on planes, mountain climbing & scuba diving as well. Just pinch your nose keep your mouth shut & blow
you could try earplugs
You can buy ear plugs that are specifically made for going under water.
Definitely try ear plugs.