Only thing more dangerous than underweighted is overweighted. But not by a few pounds. It's when someone is using 8-10 lbs or more than they really need. If you are still in class one thing that should have been covered right off the bat is how to properly weight yourself. It is the very first thing I do in OW classes after the swim tests and snorkel/free diving skills.
My procedure is as follows:
1. Put on the exposure protection you are going to be using with just your mask, snorkel, boots, and fins.
2. Take an empty weight belt and add roughly 10% of your body weight if in a 5-7 mil or heavier suit.
3. Get in the water and while I am holding onto the person's hand have them just step into the deep end from the shallow and exhale. If they don't sink add a little weight. Repeat until the just start to slowly sink. Or if they drop like a stone remove weight.
4. Next add the Scuba unit.
5. Take time to have them breathe with it by placing their face in the water to get used to it. Remind them again about equalizing.
6. Repeat the same steps as above. They should keep the weight belt on and I will either add to the integrated pockets if the BC has them, trim pockets, and/or pockets of the BC itself until the desired results occurr.
7. Once this has been done I have them layout on the surface of the water with air in the BC and in the shallow end dump air from the BC so they settle down to the bottom gently in a horizontal position.
8. If they don't we add just a couple more pounds.
9. Then just lay there and breathe to get used to the feeling of doing it.
10. Then we start working on buoyancy control. I have them breathe deeper and try to feel the increased buoyancy and decrease as they exhale.
11. Use of the inflate deflate buttons.
12. Move to the transition between the shallow and deep ends and begin work on achieving neutral buoyancy with just fin tips resting on the shallow step or slope.
13. Basic skills in this position neutral and horizontal,.
14. Swim and repeat the skills.
15. About halfway through the session we do another weight check.
16. End of session we repeat the weight check with a tank that is now around half full. And should add that here we begin to look at distributing the weights for optimal trim.
17. Document the weighting in their log.
Next session they begin with what they had at the end of the last session but I make sure I have a few tanks that are around 500-700 PSI by the end of this one so they can repeat the checks.
All subsequent sessions begin with them doing weight checks at beginning and end. So by the time we get to checkouts I expect them to know their weighting requirements and ask for the correct amount.
Now we are in a freshwater location so I do spend time going over the added requirements for saltwater. And add that their first saltwater dives should always be done in a location where they can do the checks as they have been taught before going out on actual dives.
