If diving from a boat, tell the divemaster you are going to do a weight check at the beginning of the first dive. Most divemasters can give you a pretty good approximation of how much weight you will need. Then, don’t hang back. Be the first one into the water. You may have made any needed adjustments by the time all the other divers are in the water and ready to go. There will likely be other divers making last minute weight checks/adjustments, too.