We weren't told that we could take them off when we rode Jurassic Park, but we also weren't told to keep them on. We decided to ride with them on because there was another party at the front of the boat with their masks off and we were at the back and our masks were fabric. They didn't get very wet and we just swapped out to fresh ones once we got off.
We were told on all the water rides to remove them, and then reminded when coming back in to put them back on. Ours got SOAKED on Popeyes, luckily we had backups.