Petersen has been stationed on Puerto Rico since January. He has not seen a single Navy member for a diving-related injury. The Navy is pretty serious about safety. It is drilled into your head that safety is No. 1, and the rules are rigorously enforced. It's very good training.
Tourists are another matter.
Inexperienced divers bring on trouble by diving too deep, staying too long, or coming up too fast sometimes in a panic. Spear fisherman are often tempted to push the limits, hoping to get that big lobster. It takes a lot of training, and you have to be constantly careful and aware of the safety considerations. There are a lot of knuckleheads out there who just jump in the water and go for it without knowing what they're doing. The risks include arterial gas embolus and decompression sickness.