Considering this guy was snorkeling, decompression sickness is less likely, but still possible if he has been repeatedly going deep as Nitrogen can still build up. Inner ear barotrauma is more likely in a snorkeler, and can be treated with surgery if severe. Inner Ear Decompression Sickness is caused by buildup of Nitrogen bubbles in the tissues of the inner ear, which leads to inflammation, coagulation, etc. Although a snorkeler could be subject to either of these theoretically, more would need to be known about his activities and his otoscopic examination to really distinguish between the two. Hyperbaric treatment may not cause injury in Inner Ear Barotrauma, but it is not the ultimate therapy required.
Hyperbaric treatment can accentuate the cause of the barotrauma rather than help it.
I had a patient from Germany visiting who claimed after snorkeling he had difficulty hearing and was treated with external ear drops. He went home and was told he was mistreated because he had Acute Acoustical Trauma and his hearing test did show a significant decibel loss in the high frequencies. In Europe this is apparently a recognized emergency and treated with IV infusions. I did a Medline search and sure enough they not only do infusions, but also hyperbaric treatments and pheresis. I have not heard anything like this in the US and can only imagine what the ENT call guys would say if I called them in for this.