A few years ago, I watched a History Channel story titled something like "Jellyfish Invasion." It promised to warn viewers about the huge and alarming increase in the number of deadly jellies in certain parts of the world. For this report, they sent teams to two locations suffering from the invasions of two different kinds of jellies.
The first location was Australia, which they said was beset with hordes of box jellies. They said box jelly attacks are nearly always fatal, and to prove that point, the interviewed several survivors who showed off their scars. They sent divers to multiple places in search of this invasion, but they never found a single one. On one dive, they encountered a moon jelly and hurriedly left the water, glad to have lived through the experience. They then said an approaching storm would have to cut their mission short, so they had to end that portion of the show without spotting anything other than that single moon jelly.
The second location was Japan, where they are facing an invasion of a species of jelly that grows nearly to the size of a human. These enormous jellies are causing all sorts of problems there. Unfortunately, like the trip to Australia, they were unable to find one to demonstrate the size of the invasion.
The show still concluded with a warning about the alarming increase in these deadly jellies.