"For people that haven't seen this, it's kind of disgusting," says conservationist Tony Mignucci.
But it's hard to emphasise enough how fascinatingly gross it is to watch pus explode out of a manatee's abscess as the scalpel pierces his thick skin.
The scene comes in Monday's episode of Natural World on BBC2, where David Attenborough introduces us to the people and wildlife of Puerto Rico, including a pair of rehabilitated manatees who are getting ready to go back out into the ocean.
Unfortunately the male, Aramana, has developed a nasty abscess on his back, and so a specialist vet arrives to help the team at the Centro de Conservación de Manatíes de Puerto Rico. To make matters worse, manatees don't respond well to sedation, so the whole tricky procedure must be carried out with a team of 13 people trying to stop Aramana bucking all over the place.
But when the scalpel goes in, Tony and the vet Dr Antonio are surprised at just how much pus Aramana was storing on his back. Watch the full clip, if you dare:
Where Planet Earth II showed us the brutality of nature, Puerto Rico: Island of Enchantment is a much more heart-warming affair: there's a brief clip of a boa constrictor crushing a bat to death, but (aside from the manatee pus) that's about as gruesome as it gets.
This episode of Natural World also turns the spotlight on another curious animal: the human being. In scenes to warm the heart, Attenborough introduces us to the people who are trying to make the island a better place for its endangered inhabitants.
You'll meet the schoolchildren campaigning to protect the Leatherback Turtle's hatching grounds from property developers, and the good people at the Puerto Rican Parrot Recovery Program who have successfully swelled this beautiful bird's population from 13 to more than 200. And when the manatees are ready to go back into the wild, everyone wants to help – from the National Guard, to the Department of Natural and Environmental Resources, to the police force who provide a convoy to the coast.
"The key for the future survival of Puerto Rico's natural wonders is the awakening of the island's people to its unique wildlife," says Attenborough. And as Amarana heads out into the sea with his pal Yuisa, it's hard not to feel a little bit optimistic about the future... even if you're still feeling a little queasy from all the pus.
Puerto Rico: Island of Enchantment, part of BBC2's Natural World series, airs on Monday 20th March at 9pm on BBC2