That's why it's good to carry one or more cutting tools.
Neither do I. That would be a real problem for caves. But lots of people do.
Regulator failure. Problem with an octopus is that you have to be nose to nose. Which means forget about shooting an SMB. And current/waves/surge can be an issue. This is one reason why I dive with tech gear even on rec dives. Life is just easier with a 10' hose on your primary.
Of course, if you were really greenhorns, you shouldn't have been there in the first place. Basic OW certification is 60' max. Diving beyond your training and experience is a good way for someone to get hurt.
Most of the deep stuff I do is either caves or wrecks. Depending on your location, you'll find lots of reef life in the 100-150 FSW range, but not much really deep.
Besides, if you're not a tech diver, you're limited by NDL. At 120', your NDL is 3 minutes, so what would you expect to see in 3 minutes?
Why wouldn't you have a light?
Sharks just don't bother divers. They do pass us really close to get to the food critters that are in our lights. Tarpon and other large fish do the same thing.