Surfers, especially in that geography wear wetsuits which give some buoyancy, but not like a life jacket does, and I don't know any surfers who wear life jackets.
I was a WSI, a life guard trainer back in college, still swim 5,200 yds a week which really is nothing compared to swim team, and I scuba dive down to the bottoms of our nearby lakes to set submersible pumps for a living (diving 41 years), my dive gear has a BC vest that can act as a life jacket (if) it is not damaged and (if) my regulator is functioning and (if) I have still have air in my tank and (if) I have not blacked out by like a boat hitting me, too many ifs, but I absolutely will not venture out onto surface of bodies of water on watercraft without wearing a life jacket for a whole host of reasons (surfboards are some sort of watercraft).
I assume they were more or less "drowned" in the foam, unable to breathe, suffocated.
The most professional solution for fighting most fires is foam which puts out fires by sort of drowning them too.