You can do a weight check. At the end of any shore or boat dive, when the tank is near empty, you can adjust your weighting so that your eyes are above water while still (no kicking) with a full breath, and you sink slowly when you exhale. This assures you have no buoyancy issues at the end of the dive but are not overweighted. Can also do it in a pool and make adjustments for salt water if needed, a simple formula. If your basic gear and exposure protection stay the same, you only have to do this check once because so long as you know the buoyancy characteristics of your cylinder when empty, you can then adjust for any other cylinder based on its buoyancy when empty. i.e. proper weighting with a near-empty HP steel 100 means you need 4- 5 pounds more with a near-empty AL 80. You would only have to re-do it if you have major changes in body weight, or you change your gear in a significant way such as getting new/different exposure protection).