Go for it.

 Shark dives are fun and interesting, and somewhat less dangerous than
driving on the freeway.

 Educate yourself on different types of sharkdives, and their possible
ecological impact, first.

Sharks are boring and overated. Take your ol' buds up to the PNW and get
your a.ses over to the Seattle aquarium. They got an octopus there that eats
sharks. Great fun for the whole crew!

Southern California shark dives, other than the white shark charters to
Guadalupe mentioned following your first post, are occasionally done by a
handful of local operators with the intent of finding blue sharks in open
ocean.  Often a mako will show up as well.  The "divers" sit in a cage,
usually just with snorkels not scuba gear, and the boat chums until the
sharks come in.  Therefore, your buddies don't even have to be certified
divers to enjoy the thrill of waiting endlessly for the sharks to arrive all
the while being coated in an oily, smelly fish scum.

On the charter I was on (the Aquatica), divers with a minimum of 50 dives
(their rule) could opt out of the cage and instead hang on a weighted line
at about 20 feet.  This was a much better experience.  When you get 4-6
blues circling you, it's impossible to keep your eyes on all of them at the
same time.  They give you a "shark billy", basically a filled section of PVC
pipe, that you are supposed to use to push the sharks away from you if they
come too close.  I never used mine, idiotically pushing my face up against
one as it swam by, and touching another on the tail.  But I supposedly
benefit from professional courtesy and don't recommend you try this at home.