這個標誌是危險的宣傳，它提升了瀑布暗流的神話。 如圖所示，在此瀑布中，任何其他瀑布中，甚至在海灘上都不會出現暗流。 除少數極端情況外，唯一會在大壩和水力發電廠的排水管附近找到類似水流的地方。 由於在池底沒有出口流出，因此自然界中不容易發生這種現象。 在瀑布底部或附近漂浮的困難是由於與水中混合的空氣有關的浮力的變化，而不是向下的水流。

實際上，該瀑布的流入和流出都在水池的表面。 這意味著最強的水流在水面上，最弱的水流在底部。 在一年中的大部分時間裡，幾乎沒有地下暗流。 如果您沒有在頂部看到它們，它們就不會隱藏在底部。

當河流中有大量的水流過時，瀑布的力量會在水池表面形成一個小的凹陷，導致水向該方向流動。 多數反彈並產生從池中流出的水流。 有些也從瀑布流回到瀑布下的凹陷處。 這些僅表面水流。 由於水只能從較高的高度（例如，地面）向下流動，因此它們不會在池中深處延伸。

因此，要逃開這些水流的正確方法是在它們下面游泳。 表面水流將您反覆拉出來，而不是暗流。 因此，要逃脫，您需要向水底下游泳。 這是應該在標誌上顯示的消息。 逃脫離岸流方法相同，在這裡也適用。卡住在垂直的水流中游泳，不要跟它對抗。但要在瀑布前游泳，是有悖常理的。中心的水流將帶您離開瀑布跟水池。這些訊息應該要標示在告牌上。就像在海灘告示牌上一樣，有標示如何逃開離岸流，所以這裡也應該有標示如何逃開瀑布中的水流。 但相反地，這個標誌沒有提供任何有用的訊息，實際上還具有誤導性。 這是進行水安全教育的尷尬方式。

附註1：這僅適用於一個水池範圍。 在河流中，整個橫截面都在流動，由於摩擦因素使其底部水流動仍然較慢。 而表面的水流動得更快。

附註2：颱風過後，當河流太大而超過水池的承載能力時，以上這些規則將失效。 這並不重要，因為對於任何理智的人來說，顯然無論如何在颱風過後是不要進入溪河裡。

This sign is dangerous propaganda which promotes the myth of the waterfall undercurrent. Currents as depicted in this picture do not occur in this waterfall, any other waterfall, or even at the beach for that matter. With a few extreme exceptions, the only place you will find currents like that are near drainage pipes for dams and hydroelectric power plants. It's not a phenomenon that can occur easily in nature because there is no outflow at the bottom of the pool. Difficulties with staying afloat at or around the base of the waterfall is due to changes in buoyancy related to air mixed in the water... not downward currents.
In fact, the inflow and drainage for this waterfall are both on the surface of the pool. This means that the strongest currents on the surface of the water, and the weakest currents are on the bottom. For most of the year there are barely any subsurface currents at all. If you don't see them on top... they aren't hiding on the bottom.

When there is a lot of water flowing in the river, the force of the waterfall creates a small depression in the surface of the pool, causing water to flow in that direction. The majority bounces out and creates a current flowing out of the pool. While some also flows back to the depression under the waterfall, typically from the side. These surface-only currents. They do not extend deep in the pool as water can only flow downward from a higher elevation (eg, the surface).

Therefore, the proper way to escape these currents is to swim under them. Surface currents are pulling you out, not undercurrents. So to escape you need to swim down. The same method for escaping a ripcurrent will also work here. Swim perpendicular to the current you are stuck in, not against it. It's counterintuitive, but swim in front of the waterfall. The current in the center will take you away from the waterfall and out of the pool. This is the message that should be on the sign. Just like at the beach there are signs explaining how to escape a rip current, there can be signs explaining how to escape a back current in a waterfall. Instead this sign provides no useful information, and is in fact misleading. It’s an embarrassing way to conduct water safety.

Note: This only applies to pools. In a river the entire cross sectional area is flowing, although it's still slower at the bottom due to friction. Surface water moves faster.

Note 2: After a typhoon when the river is so large as to exceed the carrying capacity of the pool, these rules breakdown. It's not important because to any sane person, it's obvious not to go into the river after a typhoon anyway.

【#重要資訊請廣傳🇮🇹】日前中國官媒、微信、香港藍媒鋪天蓋地宣傳，「武漢肺炎源自意大利」，唯一的source，就是引述意大利醫生Giuseppe Remuzzi接受美國電台訪問的一句話，再斷章取義，昨天我們已經解釋過。

一位手足為了求真，專門發電郵向Dr Remuzzi本人詢問，從這位意大利專家的以下回覆，可明確知道他的原意：不但肯定武漢肺炎源自武漢，而且懷疑早在10月尾，武漢可能已出現武漢肺炎感染，但中國政府沒有公佈，期間可能大量中國人從武漢來到意大利，令意大利出現了一些疑似案例，由於一切來自中國的資訊都不透明，才令疫情失去控制的黃金時機。整個訊息，和中國官媒宣傳的完全相反，fake news之意，莫此為甚。

Dear XXX,

The only thing I said was that some general practitioners candidly told me of having observed a few cases of severe pneumonia already in late November and December, which is not unexpected, since the majority of contagions are coming from asymptomatic people who likely travelled from China before the Chinese authorities communicated that this outbreak had occurred. Attached is my answer to the journalists who have contacted me.

//Quoting the answer:

I repeat, none of these cases have been documented as Covid-19 because there was no evidence yet of the existence of Covid-19.

In any case, we can be certain that the virus emerged in Wuhan first, where it had probably been circulating for some time before it was made public in China, and the genetics confirm this beyond a shadow of a doubt. It arrived in Italy through a German person who had been in contact with a Chinese person, as you can see in the NEJM paper (DOI: 10.1056/NEJMc2001468). The strongest evidence of the fact that the current Covid-19 derives from bats and pangolins is reported in an article in Nature Medicine (https://doi.org/10.1038/s41591-020-0820-9) recently published, which shows almost identical sequences. Commercial activities using bats and pangolins are very well documented in Wuhan market, which was almost certainly the source of the outbreak. The question now is for how long the virus was circulating in China before health authorities understood the dimension of the problem. Considering the incubation period, I would not be surprised if asymptomatic individuals had been moving around China and travelling abroad in December and maybe even earlier.

In my opinion, there is no doubt that the virus arrived in Italy from China based on genetic studies just reported in Nature Medicine. However, one has to consider the possibility that, rather understandably, the emergence of this unfortunate event in China probably occurred long before health authorities realised it,considering the number of asymptomatic carriers, which isnow extremely well documented in the paper published in Science (DOI:10.1126/science.abb3221).//

By the way, I think you should probably investigate an event that was organised in Wuhan at the end of October (see attached). We know from the paper published in Science that 80% of contagions occur through people who are asymptomatic; you can imagine how many people arrived in Italy from Wuhan in that precise period of time.
Please see also a statement by Daniel Lucey, an infectious disease specialist at Georgetown University and the Lancet paper attached.

Best regards,
Giuseppe Remuzzi//

【#重要資訊請廣傳🇮🇹】日前中國官媒、微信、香港藍媒鋪天蓋地宣傳，「武漢肺炎源自意大利」，唯一的source，就是引述意大利醫生Giuseppe Remuzzi接受美國電台訪問的一句話，再斷章取義，昨天我們已經解釋過。

一位手足為了求真，專門發電郵向Dr Remuzzi本人詢問，從這位意大利專家的以下回覆，可明確知道他的原意：不但肯定武漢肺炎源自武漢，而且懷疑早在10月尾，武漢可能已出現武漢肺炎感染，但中國政府沒有公佈，期間可能大量中國人從武漢來到意大利，令意大利出現了一些疑似案例，由於一切來自中國的資訊都不透明，才令疫情失去控制的黃金時機。整個訊息，和中國官媒宣傳的完全相反，fake news之意，莫此為甚。

Dear XXX,

The only thing I said was that some general practitioners candidly told me of having observed a few cases of severe pneumonia already in late November and December, which is not unexpected, since the majority of contagions are coming from asymptomatic people who likely travelled from China before the Chinese authorities communicated that this outbreak had occurred. Attached is my answer to the journalists who have contacted me.

//Quoting the answer:

I repeat, none of these cases have been documented as Covid-19 because there was no evidence yet of the existence of Covid-19.

In any case, we can be certain that the virus emerged in Wuhan first, where it had probably been circulating for some time before it was made public in China, and the genetics confirm this beyond a shadow of a doubt. It arrived in Italy through a German person who had been in contact with a Chinese person, as you can see in the NEJM paper (DOI: 10.1056/NEJMc2001468). The strongest evidence of the fact that the current Covid-19 derives from bats and pangolins is reported in an article in Nature Medicine (https://doi.org/10.1038/s41591-020-0820-9) recently published, which shows almost identical sequences. Commercial activities using bats and pangolins are very well documented in Wuhan market, which was almost certainly the source of the outbreak. The question now is for how long the virus was circulating in China before health authorities understood the dimension of the problem. Considering the incubation period, I would not be surprised if asymptomatic individuals had been moving around China and travelling abroad in December and maybe even earlier.

In my opinion, there is no doubt that the virus arrived in Italy from China based on genetic studies just reported in Nature Medicine. However, one has to consider the possibility that, rather understandably, the emergence of this unfortunate event in China probably occurred long before health authorities realised it,considering the number of asymptomatic carriers, which isnow extremely well documented in the paper published in Science (DOI:10.1126/science.abb3221).//

By the way, I think you should probably investigate an event that was organised in Wuhan at the end of October (see attached). We know from the paper published in Science that 80% of contagions occur through people who are asymptomatic; you can imagine how many people arrived in Italy from Wuhan in that precise period of time.
Please see also a statement by Daniel Lucey, an infectious disease specialist at Georgetown University and the Lancet paper attached.

Best regards,
Giuseppe Remuzzi//