When the lagoon water contains more washed soil which has been eroded and carried by rivers after heavy rains or cyclones, its ideal for some types of poisonous or nasty types of fish like the Jellyfish, Stone Fish (Laffe la boue in french) to come and feed on some detriments which they find "tasty". Eventually they flock closer to the shore and stay there until all the washed mud from land gets completely dispersed and the lagoon clears out.
Also, they are harmless unless stepped on or touched. They sting as a defence mechanism.
It was really unfortunate that a tourist died a couple of years ago by accidentally stepping on a Stone Fish (laffe) and I think it was at Pereybere one of the most famous beaches in the country.
And you know what!?!? She didn't die from the sting itself....surprisingly enough she died from the fact that she was allergic to the Antivenom injected to her....So sad
I never recall having heard about casualties caused by Jellyfish.
This shouldn't deter tourists visiting Mauritius because dangers are everywhere and its just your badluck that you are not at the right place at the right moment isn't it?
The STONEFISH....damn she looks like my Chemistry teacher..