A guy went in the water in the evening at Brighton Beach near Melbourne, and came out of the water with a bunch of small amphipods swarming his ankles. They started biting through his skin until he was bleeding heavily:

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Marine biologist Jeff Weir said he and others have been bitten by these creatures, but attacks are rare because people have to remain stationary for a time before they attack.

http://www.abc.net.au/news/2017-08-0...enager/8780138

If any of you mers swim in the waters of Australia's southern coast, keep moving!