Scuba divers should know their gear inside and out, as if their lives depend on it. Spoiler alert: it does!
This photo depicts an equipment problem that I have actually seen quite a few times. It is a small, non-serious (in the tropics) air leak. The simple fix is to replace an o-ring, and failure to do so results in a diver wondering why he or she is consuming so much air.
The problem is complacency. Most of the non-professional divers I see are on vacation. The dive center assembles their gear and then the gear waits for them on the boat. They put it on and perform no checks whatsoever.
Yes, it is good to be able to trust the dive center. However, people make mistakes. The person ultimately responsible for your own safety is you.
I rent my gear, but I assemble it myself. I check every release, I check both regulators, and I make sure I can deflate my Buoyancy Control Device (BCD) from every position.
Because I do this, I potentially saved four dives. Twice I had air leaking out of my gauge, and twice I had air leaking from my first stage (the problem pictured above). In all four scenarios, I was able to replace the faulty equipment before leaving the dive center. Perhaps there would’ve been spares on the boats, but that still could’ve unnecessarily delayed the dives.
So I highly recommend that every scuba diver, whether on vacation or not, get to know — and check — your gear so that you can guarantee yourself a safe and fun experience.