Mucknixer is the name given by humans to a dangerous species of drowner and drowned dead. They are different from their brothers in look. It is commonly thought that these creatures arise from the bodies of those who drown in shallow water: lost travelers falling into bogs, children who swim too far from the shore. This opinion is as widespread as it is false, for the beasts are in fact another post-Conjunction relic.
You can run into mucknixer in swamps and beaches of former Temerian province of Velen, combat tactics are basically same as for drowners. Also found at an abandoned site in Skellige.