I was picking up an oxygen when I noticed that my regulator was drawing hard breaths and I was out of gas. Just then, my buddy signaled "Emergency!" and gave me the OOG signal. I donated the reg from my mouth. The look on his face was priceless when he realized I was also OOG. I signaled, "Up! Up! Up!" and "Switch!" We switched to O2 at almost 3 ATA as we high-tailed it to the shallows.Dropping weights
Donating gas to someone with no gas — as in they cannot breathe