Lead lead scuba diving weights, 90 pounds, $2.

The newspaper ad for the yard sale said dive equipment, which made me fear the worst. And sure enough, someone had actually come out and bought the stuff the night before the sale was to be held! They left these weights for me, though.

When you consider all the heavy stuff that a scuba diver wears, it seems like he'd sink like a rock, doesn't it? Apparently this isn't the case, because scuba divers also have to wear weights to keep from floating back to the top! Remember that you can't count the air tank itself as flotation, because air tanks are designed to be as close as possible to neutral buoyancy. The average 80-cubic foot aluminum air tank, which holds about enough air to fill a telephone booth, is only about five pounds heavier when full than when empty, so its weight doesn't vary that much during a dive.

If you've ever watched a scuba diver in action, you've noticed how he appears to float along in the water without having to fight to keep from sinking to the bottom or bobbing to the top like a cork. This neutral buoyancy doesn't just happen by accident. Without constant monitoring, the diver will find himself kicking and paddling to stay in place at a particular depth, causing him to use up his air supply more quickly, thereby shortening his dive.

To maintain his neutral buoyancy, the diver starts by strapping on enough lead weight to ensure that he'll sink (normally ten percent of his bodyweight,) and then uses a buoyancy compensator vest (called a 'BC vest') to adjust his buoyancy in the water so that he remains neutral. The vest is connected right to the air tank so that the diver simply presses a button to inflate the air bladder inside the vest until he reaches neutral buoyancy. But why the heck does a diver have to keep readjusting things in the first place?

As you may know, the deeper you go underwater, the more pressure is exerted on you. The pressure exerted on us at sea level by the weight of the air in the atmosphere is known as 'one atmosphere' of pressure, or about 14.7 pounds per square inch (p.s.i.). This means that we have almost 15 pounds of pressure pushing on every square inch of us, all the time. Fortunately, we're quite comfortable with this because we have the same pressure inside of us pushing out. But at only 32 feet underwater, the pressure is already two atmospheres, or 30 p.s.i.

This increase in pressure squeezes down everything on the diver that contains air - his lungs, his mask, the air in his bc vest, the air in the bubbles of his neoprene foam wetsuit, everything - into a smaller volume. As the air volume in the diver's buoyancy compensator vest shrinks, it becomes less buoyant, making the diver heavier in the water. So, the deeper a diver descends, the more the air in his vest compresses, causing him to become heavier in the water, which makes him descend even faster.

Likewise, as a diver rises to the surface, all that air in and on his person expands, making him even more buoyant, causing him to become even lighter in the water as he rises. As you can imagine, without some means of adjusting things, scuba diving would be a miserable experience.

To maintain neutral buoyancy, the diver must constantly adjust the amount of air in his bc vest. As he descends, he adds air to the vest, and as he ascends, he lets air out of the vest. As you can see, maintaining neutral buoyancy requires an ongoing, deliberate effort on the part of the diver. But in order for it to work at all, the diver must start off in a negatively buoyant state, which is why these weights are so important.

As vital as these weights are to a diver, it's hard to imagine that mere chunks of lead could be worth more than a few cents a pound. But if you go to your local dive shop, you'll find that these lead weights sell for around $1.75 to $2.00 per pound. And since the going rate for these weights on eBay is around $1 per pound, keep your eyes open for them!

There's a very important note here about shipping heavy items like these weights. These weights are the perfect example of heavy and not worth a whole lot, which ordinarily would scare off lots of eBay bidders, because who wants to pay an arm and a leg for shipping on something that's worth only a few dollars? The only thing that made this deal worthwhile is the fact that these weights are relatively small, which allowed me to take advantage of a service you absolutely must know about: the U.S. Post Office flat rate priority shipping boxes.

The USPS flat rate boxes allow you to ship as much weight as you can fit into the box, for a flat rate ranging from about $10 to $15, anywhere in the U.S. Using these flat rate boxes, I was able to get these weights to California in three boxes of 30 pounds apiece, for a total of only $30. This was a savings of $75 over DHL or FedEx ground shipping rates, and a whopping $150 savings over what the Post Office would usually charge for priority shipping to California!

These lead scuba weights sold on eBay for $89.

Photo of lead scuba diving weights