JAKARTA residents were shocked with the presence of thousands of crawling and swimming creatures that came out of the soaked sand on the Ancol beachline to flock to any dead fish.

The creatures, body length about a half centimetre, were also found swimming in the shallow water near the shore.

A home video uploaded on Youtube showed these ferocious bug-like creatures eating up a small dead fish just thrown in to them, just like piranhas would eat up a cow thrown into the Amazon river. Within three minutes, all that was left on the Jakarta beach was the fish's skeleton.

The video clip, uploaded by an anonymous citizen, made headline news in some local television shows as well newspapers.

A private television station citing an environmentalist reported that these were sea creatures that have evolved into aggressive and stronger beings due to a tougher habitat -- the increasingly polluted sea water. A few old factories and a number illegal housing settlements in the northern part of Jakarta could be blamed for this pollution.
The ferocious-creature saga quickly caught the attention of the Jakarta municipal government's environmental control department. 
They descended on the Ancol beach to investigate. In the meantime, the creatures had earned a nickname as the Ancol monsters.

On Monday, city officials announced their findings and identified the creatures as nothing but rotten meat scavengers who also often feed on garbage littered by beach goers.

They have been around for ages, but their presence only got noticed now as their population recently surged due to an increasing food availability, ie more garbage and dead fish, officials said.

Most importantly, these creatures - with a scientific name of "isopoda cirolana" - are harmless to humans.

The number of dead fish usually increases during the transition time from dry season to rainy season, officials said.

Watch the Youtube video clip here