with perfect beaches and idyllic waters, the islands of the Bahamas are a dream destination,” says Chris Packham. “But something unexpected is taking to the water …” Cue something-unexpected-taking-to-the-water music (yeah, not so different to a certain film about a shark). And an alarmingly shaky camera to show the high level of terror about the place.

“All of a sudden these things were beginning to swim towards the boat, and I don’t know what they are, why they are in the water,” says Mike, a Canadian, who saw it for himself and somehow lived to tell the story. “I was trying to swim around them quickly and they were faster than me. They were shooting every direction, these legs, but they were swimming fast …”

Oh my God, it sounds absolutely terrifying. What the hell were they? Giant squid, perhaps? Leviathans?

Pigs! Oh. A few feral ones live on this uninhabited island. No one really knows how they got there. They’ve learned to swim out to visiting boats because the tourists feed them. Several of the hotels organise trips – there have been articles in the Telegraph, the Metro, the Mail, they’re all over YouTube. Can they really be one of Nature’s Weirdest Events (BBC2)?

Also, Mr Canadian Mike, did you really not not know what they were, these terrifying creatures swimming around you in the crystal clear waters? Perhaps the snouts were a clue, the trotters, curly tails, oink oink? Or the food scraps the boatman was throwing in the water, on the boat tour, to go and see the famous swimming pigs? Is it even that surprising that pigs can swim? Pretty much anything can swim if it has to, can’t it?

Hmm, could it be that, having reached series four, they’re running out of Weird Natural Events? A resource running low or, less politely, a barrel being scraped?

It does get a bit better. A thing called a bobbit worm that occasionally turns up in … sorry, strikes terror into aquariums, is quite fun, in a long-nasty-burrowing-wormy kind of way. Also the wasp that captures tarantulas for its babies to eat alive. What about “this mystery giant terrorising the residents of an Australian neighbourhood” though? No mystery, but a Southern Cassowary, native of the area, and just a bit bolder since its old forest home got burned down.