Thanks Water Dawg...
Here's the funny part...
The guy topside who had the extra tank was an instructor. He had an extra 10L steel tank and threw a regulator on it. He was afraid the full steel tank would not sink (!), so he strapped a weight belt to it with some lead (!) and then tossed it into the water above us. 5m down, the thing crashed next to us like an atomic bomb on the bottom, probably would have killed someone if it had hit...
Here's the funny part...
The guy topside who had the extra tank was an instructor. He had an extra 10L steel tank and threw a regulator on it. He was afraid the full steel tank would not sink (!), so he strapped a weight belt to it with some lead (!) and then tossed it into the water above us. 5m down, the thing crashed next to us like an atomic bomb on the bottom, probably would have killed someone if it had hit...