The Editor says: When it comes to Penghu dive sites, everyone immediately thinks of the Southern Four Islands — and when you think of the Southern Four Islands, you think of one thing: ferocious currents! The Wolf of Dongji is one of the most famous strong-current dive sites in the Penghu Southern Four Islands. But where there's current, there are fish — here you have a chance to see massive schools of yellowtail barracuda, and you might even run into silvertip sharks and guitarfish (southern guitarfish)! Strong currents? Bring it on! This article is contributed by Lancehsu (徐志綸)
Penghu Southern Four Islands Dive Site — The Wolf of Dongji
On this dive at the Wolf site, the current was running at 1.5 knots. The barracuda were no longer hugging the bottom, and I was able to hold my camera steady and get close enough to photograph them properly. (Editor's note: According to the experience shared by Brother Ye of Island77, once the current exceeds 2 knots, the barracuda will shelter near the bottom to escape the flow — and at that point, you simply can't capture that spectacular bait-ball-style swarm shot.)
Tides are generated by the gravitational pull produced by the positions of the sun, Earth, and moon. Because they follow fixed cycles, scientists are able to predict the timing and direction of high and low tides well in advance.
In nautical terms, the distance and speed of ocean currents are measured in nautical miles and knots. The Kuroshio Current along Taiwan's east coast brings currents of 3–4 knots in summer and 2–3 knots in winter, while nearshore currents typically run at 1–2 knots. This is why so many people ask why almost nobody dives off Taitung or Hualien — it's not that diving doesn't happen there, just that very few people do it, because the risks are extremely high. Each knot of current covers 30.8 metres per minute, 1.852 km per hour, and one nautical mile equals 1,852 metres.
Encountering a massive school of barracuda is a rare privilege — Photography: Lancehsu
1.5 Knots: Easy Diving
The Wolf site is one of the best places to feel what current is really like. At 1.5 knots or below — typically during neap to moderate tides — the barracuda gather in huge schools. You can still move forward slowly against the flow, and when you need to stop, a light grip on the reef is all it takes.
2 Knots: You'll Feel Your Heart Pounding
At 2 knots, usually during moderate tides, a diver fighting the current can perhaps hold position — but only for about 10 seconds. After that, you'll feel yourself drifting further and further from the group, and hyperventilation becomes a real risk. For beginners or anyone who has never dived in current before, this is a serious challenge.
2.5 Knots: You'll Barely Catch a Glimpse of the Barracuda
When the current reaches 2.5 knots, even kicking hard with my carbon-fibre long fins (freediving), I can barely hold my position for 10 seconds. I have to grab the reef. If I let myself drift with the current, I could be out of the Wolf zone in under 10 minutes — and the barracuda will be long gone.
Once the current exceeds 2 knots, the barracuda drop to the bottom to shelter from the flow — Photography: Lancehsu
3 Knots: Dig Deep and Pull Out Every Trick You've Got
At 3 knots — typically during spring tides — things get intense. Your second stage regulator may start free-flowing heavily; if you don't face into the current, water will flood straight into it. Your surface marker buoy (SMB) may get ripped open by the force of the flow. No matter how many times you clear your mask, water keeps pouring in. Air consumption will be far higher than normal. At this point, your dive guide, instructor, and dive buddy may all be struggling just to manage themselves. If you can't independently resolve these basic issues underwater, you could be in serious danger.
For this reason, dive shops operating in the Southern Four Islands generally require divers to hold at minimum an Advanced Open Water Diver (PADI cert) certification with 50 or more logged dives. Anything less, and you're punching well above your weight — good luck to you!
Understanding tides is the most fundamental skill for any boat captain heading out to sea. If the dive instructor also understands tides, they can anticipate current direction, the behaviour of marine life, and where creatures are likely to appear. When the captain and the instructor both know the tides and work in sync, they can take you into challenging waters and keep you diving safely — all while revealing underwater ecosystems you'd never see anywhere else.
Drift diving in strong current is exhilarating, but a dive shop that truly understands the tides can make all the difference to your safety — Photography: Lancehsu
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