>>19672215Have not heard single case when it have attacked swimmers. There are some fish who attacks though. European catfish (Silurus glanis). It can grow to lengt of 3m, and weight of 150kg. Some years ago here was case when one guy was walking a dog near our biggest river. Let dog go for a swim, while dog was still on a leash. Suddenly dog went under water. Owner tried to pull dog out, but did not managed. Instead he got pulled in direction of water. Eventually he let that leash go. It is not completely sure what happened to dog, but it is assumed that it got attacked by catfish.
Some acquaintence told that in Spain there are river named Ebra or smth, and there are warning signs that it is forbiden to swim there. Because of aggressive catfish. He and some his friends ignored warning (it was hot summer day), went for swim and got attacked. He still have bite scar on his leg.