The Queens Baths are seapools in the lava reefs below the posh, golf-course resort of Princeville on the lush north shore of Kauai. Hawaiian royalty did indeed take dips in these pools, as well as other freshwater ponds and tide pools at various locations throughout the Islands.
When seas are calm, the pools are a dream. On days like this, when 20-foot waves are exploding, they are a nightmare. These onlookers left safely, but they might not have if a rogue wave (the occasional giant among sets) came calling. Numerous fatalities have occurred here. Normally they happen on nice days, not like this one, when things appear safe but swimmers fail to take into account the rise and fall of the swells during a given day.
Always watch for at least 15 minutes before going out onto a reef; never go out on rocks that are wet with sea water; never turn your back on the waves. See the Kauai Trailblazer guidebook for more on the baths, and on ocean safety.