Common lionfish
Pterois volitans
Papua New Guinea
This is the same species that is now an exotic invader in the western Atlantic and
Caribbean.
The venom in those long pectoral and dorsal fins is reportedly extremely painful but unless you are unlucky enough to be allergic, not fatal. Luckily lionfish are not aggressive and will move out of your way. That’s a good thing because there are lots of them; they are common throughout the Indopacific and seen on virtually every night dive. They can also be seen during the day (as evidenced by this photo) but they are more active (and therefore more noticeable) at night. They normally hang out inside caves, under ledges or coral heads, next to submerged logs, and around wreckage. Small juveniles will hide inside the arms of branching coral.