Diving in fresh water is extremely boring. It is tediously monochromatic. Lakes are as still as swimming pools and devoid of the interesting surge presented along the California coast. The only thing caves add is rocky relief and danger, particularly at the depths indicated, viz. 67 and 127 feet.
Twin tanks might seem safer to the layman, but in reality multiply the danger.
1. There is increased risk of going too far, too deep, staying too long.
2. There is increased risk of decompression sickness. You can hardly get in trouble with a single 72 cu ft tank.
But with twins, it's much easier.
3. Going deeper presents the risk of nitrogen narcosis, or giddiness. You get disoriented, confused. It's like
vertigo, which I also experienced as a pilot when ground cover socked me in on takeoff/climbout.
He had no business doing this to his 15 year old son. Both paid the price for dad's stupidity.
In hundreds of ocean dives, I never saw so much equipment on anybody as both of these guys have. It presented a very false
sense of security and safety, as we now see. Once in danger, you can easily dump your tank and free ascend from even 100 feet down.
They did not even do that. Most divers who drown are still wearing their weight belt. They don't want to pay for a new one.