On May 11, 2020, five surfers drowned after asphyxiation in a massive foam bank near the Dutch coast. We present a detailed account of the event and an examination of factors that govern local foam events, that are traditionally caused by Phaeocystis globosa (Prymnesiophyceae). The data support the hypothesis that the foam originated from a Phaeocystis bloom which if correct would make this accident the first report of human fatalities due to a harmful algal bloom in The Netherlands, and the first globally due to a Phaeocystis bloom. The rarity of massive foam banks and the absence of local real-time plankton monitoring makes it difficult to accurately predict dangerous situations as in 2020. As a prevention, surfers and other water sportsmen need to apply good seamanship during stormy and foamy conditions.

2020 年 5 月 11 日，五名冲浪者在荷兰海岸附近的一个巨大泡沫堆中窒息而亡。我们详细介绍了该事件，并对控制局部泡沫事件的因素进行了检查，这些事件传统上是由球形棕囊藻（Prymnesiophyceae）引起的。这些数据支持泡沫起源于棕囊藻华的假设，如果正确的话，这起事故将成为荷兰首次因有害藻华造成的人员死亡报告，也是全球首例因棕囊藻华而死亡的事故。由于大量泡沫堤的稀有以及当地缺乏实时浮游生物监测，因此很难像 2020 年那样准确预测危险情况。作为预防措施，冲浪者和其他水上运动员需要在暴风雨和泡沫条件下运用良好的航海技术。