For example the video you linked is of a Chinese boat operating ~350km off the coast of Argentina, which is nearly the opposite side of the world from China.
In contrast, the waters claimed by China in the South China Sea are just off the coast of Vietnam, Malaysia, Indonesia, and the Philippines, and not in close proximity to China [1]. The Permanent Court of Arbitration has also ruled that there is "no legal basis for China to claim historic rights" over the nine-dash line.[2]
They are however, very conveniently located over a large number of unexploited oil and gas deposits.
[1] https://en.wikipedia.org/wiki/Territorial_disputes_in_the_So...
[2] https://en.wikipedia.org/wiki/South_China_Sea#2016_ruling
https://www.youtube.com/watch?v=00rMVee0R4c
And there are examples from other countries too.
This is just the first example but you can find many more:
https://www.youtube.com/watch?v=E3lkM4t8AaA