This small passerine bird is a species found in wet sedge beds with vegetation shorter than 30 cm (12 in).

Drainage has meant that this species has declined, and its stronghold is now the Polesie region of eastern Poland and south Belarus, where 70% of the world's population breeds.

It can be confused with the juvenile sedge warbler, which may show a crown stripe, but the marking is stronger in this species, which appears paler and spiky-tailed in flight.

[5] The aquatic warbler is the rarest and the only internationally threatened passerine bird found in mainland Europe.

The MoU covers 22 range States (Belarus, Belgium, Bulgaria, France, Germany, Hungary, Latvia, Lithuania, Luxembourg, Mali, Mauritania, Morocco, the Netherlands, Poland, Portugal, Russian Federation, Senegal, Slovakia, Spain, Switzerland, Ukraine and United Kingdom).

As the late-cut grass isn't suitable for feeding making these measures economically unfavorable, farmers who agree to help out receive state issued compensations.

[10] By the end of the 2019 summer breeding season, 11 (22%) of the translocated birds returned to the Žuvintas biosphere reserve.

[11] In the summer of 2019, the BEF successfully translocated, raised, and released an additional 50 birds from Zvanec Belarus to the Žuvintas biosphere reserve.