Sit on the bow of a liveaboard as it clears the last of the Khao Lak headlands before dawn, and the Andaman opens ahead of you in a way it simply doesn't from a Phuket day boat. By the time the sun breaks the horizon, the Similan Islands are still four hours north — but the water around you has already changed. It's deeper, bluer, and moving. The GPS chart shows bottom at 45 metres, then 80, then the screen blank of open ocean beyond the shelf. This is what the Similans offer: genuine offshore water, some of the best-preserved reef in the region, and a fishery that rewards the angler willing to travel out and stay a few days to learn it.
The Similan Islands — officially Mu Ko Similan National Park — are a chain of nine granite islands (the name comes from the Malay sembilan, meaning nine) located approximately 70 kilometres northwest of Khao Lak. They are, without question, one of the most beautiful island groups in the Andaman, and their protected status reflects a Thai government commitment to their preservation. That protection defines the fishing here in specific ways that every visiting angler needs to understand before they arrive.
What and Where
The Similans sit on a granite shelf that drops steeply into the deep Andaman basin on the western side and more gradually toward the Thai coast on the east. This topography creates a concentration of productive fishing habitat: the western walls of the islands are swept by Andaman swells and open-ocean currents, pushing up nutrients and holding bait. The deeper water to the west and between the islands harbours both the reef-associated species that draw dive boats and the mid-water pelagics that draw sportfishers.
The park encompasses the nine main Similan islands plus the adjacent Koh Bon and Koh Tachai to the north, which are technically separate but often included in extended liveaboard itineraries. North of Tachai, the Surin Islands are a further extension that some liveaboards incorporate on week-long trips.
The departure gateway for Similan liveaboards is Tap Lamu pier, the purpose-built national park gateway south of Khao Lak. Day trippers (primarily divers) also depart from here. From Tap Lamu to the southern Similan islands is roughly a three-hour run, and the transit is typically done overnight to maximise fishing time.
Marine park boundaries
The Mu Ko Similan National Park covers the islands and a defined marine zone around them. Fishing within this zone is prohibited. Liveaboard operators who know the grounds fish outside park boundaries — in the open water to the west and on structure that falls outside the protected area. Confirm with your operator that they understand and respect these limits.
The Species Mix
The Similan area's headline sportfishing targets are giant trevally, dogtooth tuna, wahoo, and a range of mid-water pelagics. The GT fishery here is among the best in Thai waters, with fish in the 25–50 kg class realistic, and larger specimens documented. They associate with the granite pinnacles and rocky points of the islands, and the combination of clear water and bold structure makes for exceptional surface popping.
Dogtooth tuna (Gymnosarda unicolor) are the primary jigging target and one of the most technically demanding fish in the Andaman. Built for explosive acceleration, they'll descend into structure on the first run with a speed that leaves anglers who aren't prepared to apply maximum pressure watching their braid disappear. Dogtooth in the 20–40 kg range are catchable on the deeper western walls; fish over 50 kg are present and occasionally landed.
Wahoo (Acanthocybium solandri) are a highlight of liveaboard Similan trips — fast, aggressive, and spectacular on trolling tackle. They tend to concentrate around current lines and drop-offs rather than hard structure, and the best wahoo action often happens during transit between islands rather than at anchor.
Yellowfin tuna pass through the Similan area, particularly during the peak dry-season months when bait concentrations are highest. They're not the consistent daily target that dogtooth tuna are, but when a yellowfin school is located — typically on the surface chasing flying fish — they're accessible to topwater and trolling approaches.
The reef itself holds coral grouper (Plectropomus leopardus), squaretail coral grouper (Plectropomus areolatus), bluefin trevally, red bass (Lutjanus bohar), yellowtail fusilier and various snapper species. The reef-fish community inside the park is visibly healthier than reef systems further south that face more commercial pressure, a direct result of the no-take protection.
Season and Conditions
The Similan liveaboard season tracks the northeast monsoon precisely: October 15 through May 15 is the official park open period, though the exact dates vary slightly by year based on conditions. Outside these dates, access to the national park zone is prohibited.
Within the season, conditions vary significantly. October and early November can see residual swell and occasional squalls as the monsoon transition completes. December through February offers the most settled conditions — flat mornings, light northeast breeze, excellent visibility underwater and on the surface. March remains good, with increasing afternoon cloud. April sees the season narrowing as southwesterly conditions begin building.
Water temperature in the peak season sits around 28–30°C at the surface. The granite-boulder habitat of the Similans creates complex underwater topography that holds temperature gradients, and dogtooth tuna in particular are often found where these gradients concentrate bait.
The Similan Islands offer something increasingly rare in Southeast Asian waters: a reef system large enough and protected enough that the fish populations actually reflect the habitat quality.
The Trip — Day Boat vs Liveaboard
This is not really a debate in the Similans context: the fishery is a liveaboard fishery. From Phuket, the Similans are about 100 kilometres north — a three-hour boat ride each way from Chalong Bay, or two hours from Tap Lamu. Running that distance on a day charter leaves four to five hours of actual fishing time at destination, which is rarely enough to locate the best structure, fish it at the right tidal stage, and work through the session properly.
A three- to four-day liveaboard gives you the ability to spend full days on the grounds, fish the dawn and dusk windows when GT and pelagic activity peaks, and move between islands to find the best current and conditions on a given day. The economics also work out — a Similan liveaboard typically costs 1,000–2,000 USD per person for four days, inclusive of accommodation, most meals, and guide/deckhand support. Compared to multiple day charters from Phuket that barely reach the grounds, the liveaboard is clearly better value for serious anglers.
Some Khao Lak-based operators run long day trips to the southern Similans — feasible on calm days, but exhausting and limited. For most anglers, these are a last resort rather than a plan.
Extended liveaboards of six to eight days that include the Surin Islands and push north toward the Myanmar border exist and are worth considering for anglers with the time. The Surin Islands add a different habitat to the mix — shallower, more mangrove-influenced in places — and the Myanmar bank beyond has barely been touched by sportfishing.
Techniques
Surface popping is the primary method for GTs around the Similan Islands, and the conditions are ideal: clear water, visible structure, and fish that can be spotted before the cast. The standard approach is to work the rocky points and submerged boulders on a rising tide, fan-casting poppers across the face of structure and working them aggressively back. Stickbaits (slow-sinking pencils) are increasingly popular for pauses over structure that holds GTs tight.
Vertical jigging is the method for dogtooth tuna and is typically done from the boat at anchor or drifting over known drop-off structure. High-speed jigging with 250–350 gram jigs worked fast through the water column produces the aggressive strikes dogtooth are known for. Slow-pitch jigging has also proven effective, particularly for grouper and amberjack that share the same pinnacles.
Trolling during transits between islands covers wahoo and yellowfin opportunities that would otherwise be missed. Experienced operators run two to four lines during every island-to-island move, and it's not uncommon for the best fish of a trip to come on a transit troll rather than at an anchor spot.
Live bait fishing is effective for GTs and various pelagics but requires maintaining live bait aboard — scad and hardyhead are the typical choices. Not all liveaboards maintain live bait tanks, and it's worth confirming this before booking if live bait is a priority in your technique mix.
Tackle That Works
The Similan GT fishery demands heavy spinning gear: rods rated 80–120 lb, matched with reels in the 18000–25000 class and 100–120 lb PE braid mainline. Leaders of 100–150 lb fluorocarbon in 60–80 cm lengths are standard. Poppers and stickbaits in the 150–200 gram range are the working sizes. Hooks must be heavy-gauge assist hooks on jigs, and split rings should be upgraded on any lures before the trip — standard factory hardware is often inadequate for Similan-class GTs.
For jigging, a dedicated jigging rod rated to 300–400 grams paired with a high-capacity reel (spinning or conventional) holding 300+ metres of PE 4–5 braid is the minimum. The dogtooth tuna's first run after a strike is one of the most violent events in sport fishing — gear that isn't rated for it will be destroyed. A quality drag system that can be locked down hard is non-negotiable.
For trolling wahoo and tuna, 30–50 lb class outfits with wire or heavy fluoro leaders for wahoo (whose teeth will cut mono and light fluoro in a single bite) are appropriate.
The Operator Landscape
Quality liveaboard operators for the Similan fishing run a narrow field. Look for vessels that are set up specifically for fishing — outriggers for trolling during transits, a live bait well, proper rod storage and rinse facilities, and a captain who can discuss where they'll be fishing relative to the park boundaries and tidal windows. A crew that understands GT popping technique (calling casts, directing anglers to structure) is worth substantially more than one that puts you on the bow and leaves you to it.
Vessel size matters here. Smaller, purpose-built sportfishers can anchor closer to productive structure and move more nimbly than converted larger vessels. But larger vessels offer more comfort over multi-day trips in sometimes uncomfortable weather. Experienced anglers prioritise fishing capability; newer anglers might weight comfort more.
Ask specifically about electronics: quality depth sounders and GPS chart plotters loaded with Similan waypoints are the difference between finding the fish and motoring around. The best captains have years of personally marked fishing spots on their plotters.
Conservation and Ethics
The marine park protection around the Similans is meaningful and should be treated as such. Beyond the legal requirement to fish outside park boundaries, there are ethical dimensions that serious anglers take seriously.
GT catch-and-release is standard practice among quality operators in the Similan area. GTs are generally photographed at the boat and released — the fish is not brought aboard, which reduces stress and increases survival rates. Jaw-gripped lifts at the surface are the norm.
Dogtooth tuna are typically taken for consumption, but there's no conservation reason to take every fish landed. Given the depth they're worked from, dogtooth often suffer barotrauma and may not survive release in any case — this is a fishery where retention is more defensible than for surface-caught species. Fish you can't use, you shouldn't take.
The reef ecosystem around the Similans is a conservation success story. Keep it one by not anchoring on reef, not handling reef fish unnecessarily, and not fishing inside the park boundaries regardless of what other vessels may be doing.
Where to Go Next
The Similan Islands fit into a broader Andaman saltwater picture. These guides complete it:
- Andaman Sea fishing guide — the full overview of Thailand's Andaman fishery
- Liveaboard fishing in Thailand — how to choose and book the right vessel
- GT popping tackle guide — full breakdown of the gear you need for Similan GTs
- Saltwater jigging rods Thailand — choosing jigging gear for dogtooth and amberjack
- Khao Lak — the land-based logistics hub for Similan liveaboards
