'Pitch black, you can't see the bottom': Ontario cave diver watches Thai rescue unfold

The death of a former Navy SEAL, who ran out of oxygen trying to free a boys soccer team trapped in a cave in northern Thailand, highlights the dangers posed by this rescue operation.

A dive master in Thunder Bay, Ont., who has been watching the drama unfold, believes the key to successfully saving the group will be ensuring the players remain calm during the long underwater swim to safety.

• Thai rescuers fight water and oxygen levels in cave as diver dies

The darkness, and being in a confined space for a prolonged period, can easily cause people to panic when they're diving in caves, said Len Mason.

"It's pitch black, and you can not see bottom and your depth perception is off and there is a little bit of panic that you need to keep under control to get to your destination," he said, recalling a cave dive he did in Palau, in the Pacific Ocean.

'Follow your bubbles'

"I knew I was going down to about 100 feet, and then going up into a cave and the only thing you can trust is your computer, to know when it's time to turn, and your dive light," he said.

As well, dark conditions can often be confusing for divers, as they may become disoriented, and have difficulty distinguishing up from down.

Mason advises divers to remember that "your bubbles will always rise, so follow your bubbles."

The current flowing through the underwater tunnels also poses a significant challenge, he said. Diving with the current is "fine. The current should be slowly pushing you out. That's a nice comfortable dive."

However, as the current becomes stronger, so too the dangers.

'You can go through your air real fast'

"You will lose control and the current can toss you into obstacles. If you're going against the current, you're kicking harder, you're breathing harder, you're in a cardio situation and you can go through your air real fast" said Mason.

Increasing the speed of your breathing could mean draining your oxygen tank sooner, or spitting out your regulator, and possibly taking a big mouthful of water.

If authorities decide the only way to help the team and their coach escape the cave is by diving, Mason believes communicating the dive plan will be crucial.

Keep them calm, 'trusting their rescuer'

"That way they know going in, 'Okay it's going to be a rough ride'," he said. "I would be telling them 'Remember to breathe and trust me, I'll have you the whole way.' The main thing is keeping them calm and trusting in their rescuer."

The 12 players and their coach have been trapped since June 23.

You can hear the full interview on CBC's Superior Morning here.