Cave diving is dangerous and MUST NOT be attempted unless you have formal cave diving training from a reconized agency. IANTD, NSS-CDS, NACD and GUE (among others) offer formal cave diving training.
Even with training, you can be killed cave diving.
For more information see the NSS-CDS's Saftey Broshure.
The final dive in our cave class was a double stage scooter dive in Nohoch Nah Chich to the Blue Abyss, 10,000 feet from the main entrance.