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- I carry too much lead
What is happening
You sink quickly, then add a lot of gas to the BCD to stop, but buoyancy remains unstable. You may swim more upright, feel more drag and use more gas.
Why it happens
Ordered from the most common cause down. Open one to see the mechanism behind it.
Beginners are often given more lead than they need. It makes the initial descent easier but then requires BCD gas compensation throughout the dive.
- an inherited course or rental setup
- wanting to descend quickly
- no individual weight check
The gas in your cylinder has mass, and cylinder buoyancy changes as you breathe it. Your weighting must be sufficient for the end of the dive, not only the start.
- a different cylinder material
- setting up only at the start
- an unfamiliar rental cylinder
Water density and the buoyancy of an exposure suit change the weight you need. A setup from fresh water or a different suit should not be carried over automatically.
- moving between fresh and salt water
- a different wetsuit thickness
- a different BCD or cylinder configuration
Adding lead does not fix poor trim or a BCD that has not been fully vented. It increases the gas volume needed for compensation and can worsen your position and drag.
- lead for a faster descent
- lead for an upright position
- not fully venting the BCD
What to try on your next dive
One thing, not ten. Give it a full dive before you judge it.
Surface weight check in your full configuration
- Enter water that is too deep to stand in wearing your full configuration for the day.
- Fully deflate the BCD.
- With a normal breath, check that the water is at eye level.
- Exhale calmly; you should begin to sink. Adjust in small increments and repeat the check.
- Check that your weight-system quick release is accessible and secure.
- Confirm your setup near the end of the dive with an almost empty BCD.
How you will know it is working
| Published reference | Value | Source |
|---|---|---|
| Surface criterion | water at eye level on a normal breath; sink on exhalation | DAN — Weight Up! |
| Fresh-to-salt-water adjustment | about 1.8 kg | Dive Training — Pre-Dive Weight Check |
Check in deep water with no gas in the BCD and in your full dive configuration. Repeat the test after any change in equipment or water type.
- Do not treat underweighting as the safe error; in a drysuit it can cause squeeze and loss of insulation.
- Check your weights and their quick release before every dive. Unintentionally losing weight can cause a rapid, uncontrolled ascent.
- Overweighting increases decompression stress; it is not merely uncomfortable.