Hydrilla verticillata 1 Sila ezers, Latvia 100712 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Hydrilla verticillata 2 Sila ezers, Latvia 100712 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Hydrilla verticillata 3 Sila ezers, Latvia 100712 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Hydrilla verticillata 4 Sila ezers, Latvia 100712 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).