The Editor says: Every summer, as water activities grow more popular and more outdoor enthusiasts take to the water, tragic incidents appear in the news with increasing frequency. Without a solid understanding of the ocean, even seemingly calm waters can hide serious risks. That's why knowing how to assess sea conditions is a fundamental skill every person should have. This article is adapted from Li Zhengwei's personal Facebook page.
Over the past couple of days, more people have been asking about courses, and many have brought up water safety. Just this morning, a parent told me she'd been swept out by a current at Xiaoliuqiu — it terrified her.
Essential Safety Knowledge for Water Activities
Many people actually misunderstand what makes a body of water dangerous. To be precise, assessing a dangerous sea area isn't just about location — it also involves tides, currents, and wave height. When sea conditions are good, anywhere is safe. When conditions are bad, anywhere is dangerous. Before heading into the water, check the following basic information to stay safer!
Real-Time Outdoor Sea Conditions
Central Weather Bureau Real-Time Marine Conditions Website. This site lets you check sea temperature, wave height, and wave period. For the Northeast Coast, look at the Changtan Li (near Chaojing) and Longdong stations.
Sea temperature is mainly related to currents. Sunlight only warms the top 30–50cm of the surface, so use the sea temperature reading to decide what thermal protection to prepare.
Wave height should always be read alongside wave period. A wave period greater than 6.5 seconds makes conditions unsuitable for entering the water; greater than 8 seconds means long swells are present — typically caused by typhoons or the northeast monsoon. If wave height is low but wave period is long, there are long swells offshore. Be alert to potentially stronger currents and the increased difficulty of entering and exiting the water — beginners especially need to take note.
If you're heading to an outlying island, also pay attention to wind direction. Taiwan has relatively few marine weather buoys, so you can only reference nearby buoy data or use Windy to estimate probable wind direction. Because outlying islands are roughly round in shape, the windward side will have larger waves while the leeward side stays calm. Recently, southwesterly winds around Green Island have been strong, so the northern and northeastern sides will be relatively calm.
Understanding Tides
Many people ask me whether they need to check the tides. For surface activities like snorkeling and SUP, tides are actually relatively less important. Most people assume that low tide — when the water is shallow — is safer, but it's actually the opposite: deeper water is less likely to cause injury, while shallow water is where waves can throw you tumbling over reef rocks. One important thing to watch out for, however, is that around the time of high or low tide each day there is a slack period. If conditions seem calmer during slack tide and you get in the water, the tide may turn after a while and waves can pick up, making it harder to get back to shore.
For scuba diving, however, it is recommended that you consult the day's tide tables to assess incoming and outgoing currents, as well as the associated risk of reduced visibility caused by suspended sediment. At Chaojing, for example, an incoming tide can cause water temperature to plunge 2–3°C almost instantly, and visibility can drop to under 30cm — conditions that pose a real risk for scuba diving.
Ocean Topography
Generally speaking, bay (headland-bay) terrain is relatively safe: within an indented bay, currents are usually weaker and waves calmer. Protruding headlands, on the other hand, tend to have stronger currents. Even in large bays such as Longdong Bay, the areas near the two flanking headlands can be relatively hazardous — entries and exits around Hemei become very difficult if waves pick up. And if both the wave direction and wind direction are aimed straight into the mouth of a bay, the interior won't be calm either.
Most water activity accidents come down to a misjudgment of one's own abilities. Because most people lack experience in open-water environments — whether the ocean or rivers — they tend to overestimate what they can handle. It's not that open water is inherently terrifying; rather, rigid competition-style swim training places too much emphasis on stroke technique, leaving swimmers unable to adapt to a changing environment. Not looking where you're going makes it easy to lose your bearings, and mechanical movement patterns and breathing rhythms increase the risk of swallowing water.
Swimming must be an active, adaptive skill. Let children engage with the ocean from a young age — even just wading knee-deep helps them develop a feel and comfort for the water. That adaptability greatly increases their safety. Get in the water often, accumulate ocean experience, and you'll naturally learn what's safe and what's dangerous. In unfamiliar waters, go with an experienced dive guide. Most importantly, don't push your own limits lightly — respect the ocean and every living thing in it, and respect your own life!
Stay safe out there, everyone!
Cover image: Photo by Leo Rivas on Unsplash
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