A.) Plenty of people knew Spivey was cave diving without a cave cert. Plenty of people knew Spivey was taking Sanchez diving, without any cert. The math is pretty easy to do. But in case that's still hard to fathom, they were both posting about their exploits - including pictures - on FaceBook and cave diving forums. Unless people thought they were going to dive the pool at LR - which I believe is about 10ft deep - with all this gear...
B.) As to whether Spivey was doing anything illegal, well, he dodged that bullet by killing himself. Had he survived, the Florida statute for "aggravated manslaughter of a minor" could have probably applied. described in Florida 782.07 as follows "A person who causes the death of any person under the age of 18 by culpable negligence under s. 827.03(2)(b) commits aggravated manslaughter of a child, a felony of the first degree." (827.03 specifies culpable negligence as "An intentional act that could reasonably be expected to result in physical or mental injury to a child.")
I think you could produce a line of expert witnesses out the door to testify that a diver with no cave training or certs, taking an uncertified minor cave diving, particularly at Eagle's Nest, without proper training, gear, breathing gas mixes, or adequate gas supply would clearly meet the burden of "reasonably be expected to result in injury."