Giant Trivially (GT)
What:
If there's one fish that sits at the top of every diver's bucket list, it's the giant trevally. These things are absolute tanks — pure muscle wrapped in silver armor with the attitude of a freight train. GTs are the largest member of the jack family and are the undisputed apex predators of tropical reefs. They can grow well over 100 pounds and reach lengths past five feet, though most fish divers encounter are in the 20 to 60 pound range. The IGFA all-tackle world record sits at over 160 pounds caught off Japan, so these are serious fish. They're known by different names around the world — Ulua in Hawaii, Giant Kingfish in Australia, and just "GT" pretty much everywhere else. Their body is thick and compressed with a steep forehead, powerful tail, and coloring that ranges from bright silver to dark charcoal depending on age and environment. Older males can turn almost completely black. GTs are voracious predators that eat fish, crustaceans, octopus, and have even been documented eating seabirds off the surface. They hunt in packs, patrol reef edges, and are known for explosive ambush strikes that will make your heart stop.
Where:
Giant trevally are found throughout the tropical Indo-Pacific region, from East Africa and the Red Sea all the way across to Hawaii, Japan, and northern Australia. They are not found in the Atlantic, so if you want to shoot one, you're heading to the Pacific or Indian Ocean. Hawaii is the most accessible destination for US-based divers — the Hawaiian Islands have a deep cultural connection to the ulua and offer solid opportunities on all the main islands. Beyond Hawaii, the top GT spearfishing destinations include Australia's Great Barrier Reef, the Seychelles, the Maldives, Oman, Christmas Island, and various atolls throughout the South Pacific. GTs prefer clear coastal water around reef edges, lagoons, channels, drop-offs, and rocky structure. Juveniles start in estuaries and mangroves before moving offshore as they grow. Look for them on the outer edges of reefs where current pushes through channels and around isolated coral heads — anywhere that concentrates bait. They patrol these zones like wolves.​
When:
GTs are warm water fish and are generally active year-round in tropical locations, but timing your dive matters. They are most active during moving tides — incoming or outgoing water that pushes bait across reef edges and through channels is prime time. Dawn and dusk are the peak feeding windows, though they'll strike any time conditions are right. In Hawaii, the summer months bring warmer water and better visibility for targeting ulua. In Australia and the Seychelles, October through May is generally the best window when seas are calm and water clarity is optimal. Full moon and new moon periods that create stronger tidal movement tend to produce more GT activity around reef structure. Pay close attention to local regulations wherever you dive — in Hawaii, ulua have specific rules, and in many destinations GTs are strictly catch-and-release or protected entirely. Always check before you shoot.
Tips:
Let me be real with you — hunting a GT underwater is one of the most intense experiences in spearfishing. These fish are fast, powerful, and smart. They will test every piece of your gear and every ounce of your composure. The biggest mistake divers make is being underprepared with gear that can't handle the fight. You need a serious speargun for GTs — a large railgun or roller gun in the 120 to 150cm range with heavy shaft and at least double bands. Your shooting line and reel need to handle the explosive run that's coming the second you pull the trigger. A breakaway setup with a float line and hard float is strongly recommended because these fish will drag you into the reef if you're attached directly.
Shot placement is critical. The kill zone is right behind the gill plate along the lateral line — you want a stone shot that anchors in the spine or hits both gills. A gut shot or tail shot on a GT means you're about to lose your shaft, your rig, and possibly your pride. These fish will head straight for the reef the instant they feel the shaft and will cut your line on coral in seconds. Mark Healey, one of the best watermen on the planet, has talked about how even with a sling and three-prong, landing a GT requires knowing exactly where they'll be, approaching from the right angle, and staying calm after the shot instead of panicking.
Your approach needs to be calculated. GTs are curious but they're also wary. Use reef structure for cover and let them come to you when possible. Avoid aggressive movements — stay relaxed and let the fish close the distance. If they're patrolling a reef edge, position yourself along their path and wait. Flashers and chum can attract them but in clear water they may spook if something feels off.
One more thing — GTs are not great table fare and are known carriers of ciguatera toxin in many areas. Most experienced divers practice catch-and-release with GTs, shooting only for a true trophy or personal milestone. If you do take one, do your research on ciguatera risk for that specific location. These apex predators are essential to reef health and they deserve respect. Shoot one, get your photo, and let the rest patrol the reef.
Tips:
As mentioned above, the best way to find halibut is during grunion run at night in shallow water. Obviously, you will need a flashlight and the proper speargun. For Halibut, you do not need a long speargun at all. My biggest halibut to date was 42" long and 33 pounds. I actually stab the fish with a 18" long metal poker while I was diving at work. The point is that the fish allowed me to swim right up to it. Also, just use a regular flopper shaft, no need for a slip tip because you will be shooting into the bottom. Be patient! Halibut hunting requires you to cover a lot of ground and because these fish are so well camouflage lying on the bottom, you should swim slowly.