What you're hearing is the collective sound of men everywhere crossing their legs and squirming.
Swedish authorities have warned men off swimming in the nip after an Amazonian fish known for having a taste for testes was found by a fisherman in the Oresund Sound between Sweden and Denmark. The pacu fish is a relative of the piranha and comes with a fierce set of teeth that are just not pretty to look at, and is lovinlgy nicknamed 'the ball cutter'. Cute.
Pacus can grow up to nearly a metre in length and men have been known to bleed to death after losing their dangly bits in the Amazon thanks to the snap happy and hungry fish.
Denmark's National History Museum cautioned everyone saying 'Keep your swimwear on if you're bathing in the Sound these days - maybe there are more out there! The pacu is not normally dangerous to people but it has quite a serious bite, there have been incidents in other countries, such as Papua New Guinea where some men have had their testicles bitten off.'
Only one fish was found in the strait and officials are currently awaiting results to confirm it is a pacu before telling people not to swim at all, but we're 99% sure that you'd just have to show this picture to any Scandinavian man and that'd do the trick.