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If you ever noticed that the ocean looks like it's full of 'square waves' - it's best to get out of the water immediately.
The phenomenon is known as cross seas and it's something that is considered extremely dangerous.
This is because the quadrilateral-shaped pattern is created when two separate weather systems collide that are moving in different directions.
As a result, this makes them very similar to rip tides which are a struggle to get yourself out of. If you find yourself attempting to swim in cross seas, you would be fighting two different waves simultaneously.
In a recent Reddit post, people were discussing the wave formation. For many this was the first time they had ever seen or heard of cross seas, with one person writing: "Amazing. I have been stumbling over this planet for half a century and I have never heard of square waves. I know so little about everything."
Someone else explained: "These are long-period swells caused by weather systems actually far apart from each other. The swells generated by those systems were at this angle to each other. They then travel sometimes long distances and can eventually collide like this."
A third added: "They are actually quite dangerous," while another subbed them the 'most uncool and unhip waves in the ocean'.
Another ocean phenomenon that was spotted in December was a huge multiple-vortex waterspout, swirling over the surface of the sea.
The incredible natural phenomenon was seen by Gilad Raz in Caesarea, Israel, on 17 December and images show the waterspout swirling over the ocean, edging its way towards the coast.
The waterspout is made up of a single smaller vortex in the centre of the structure and a large hollow one that spun around it making it look even more ominous.
The incredible footage was captured by Frank LeDay, who shot the waterspouts far out at sea. He wrote: "Wow!! Ever see six waterspouts at once?"
The awe-inspiring phenomena came at a time when Storm Marco and Storm Laura threatened the US, with the latter killing at least 24 people in Louisiana and Texas.
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