Spearfishing in Marine Park is a NO NO. Are they spearfishing for money? The person in picture do know about his target, and the fish, is a giant "Lou Shu Pan" a.k.a Kerapu Tikus looks so big and good...It is expensive in restaurant and very tasty... 
Hi evo, this is not a Lou Shu Pan aka Barramundi Cod but a Loong Dhan aka Grouper or Epinephelus sp. A barramundi cod looks like this:-

......and it's becoming rarer than jewels now. When you conduct a Reef Check, this specie will be listed in the Fish Transect to indicate the health of the reef if you do see one. A lot of marine fish are bio-indicators which divers fail to realise the detriment they can cause if they take them out immaturely. For instance, groupers are protogynous hermaphrodites, having the female reproductive organs come to maturity before the male. When threatened or the male is taken out of the harem, the largest, most dominant female in the group will change sex to become a male.
When someone hunt on a reef, not only are the largest fish removed from the population, but the social/threat cues that trigger sex change are interrupted. Thus, fishing that concentrates on aggregations results in smaller fish with fewer eggs, and ultimately leads to loss of males. This is compounded by loss of fish that are changing sex because they act more like males than like females and are thus more vulnerable to capture. No males, no sex, no babies, no fish. Do we want that? Protecting males and grouper populations (or any big reef fish) in general should be profound because protecting males means protecting specific habitats where males reside, and because protecting populations involves protecting spawning sites. These sites often form the very heart of the marine parks.
Would this reason be justified enough to report hunters in our sanctuaries???