Water rail – Rallus aquaticus
is a bird of the rail family which breeds in well-vegetated wetlands across Europe, Asia and North Africa. Northern and eastern populations are migratory, but this species is a permanent resident in the warmer parts of its breeding range. The adult is 23–28 cm (9–11 in) long, and, like other rails, has a body that is flattened laterally, allowing it easier passage through the reed beds it inhabits. It has mainly brown upperparts and blue-grey underparts, black barring on the flanks, long toes, a short tail and a long reddish bill. Immature birds are generally similar in appearance to the adults, but the blue-grey in the plumage is replaced by buff. The downy chicks are black, as with all rails.

The adult of the nominate subspecies is a medium-sized rail, 23–28 cm (9.1–11.0 in) long with a 38–45 cm (15–18 in) wingspan. Males typically weigh 114–164 g (4.0–5.8 oz) and females are slightly lighter at 92–107 g (3.2–3.8 oz).[20] The upper parts from the forehead to tail are olive-brown with black streaks, especially on the shoulders. The sides of the head and the underparts down to the upper belly are dark slate-blue, except for a blackish area between bill and eye, and brownish sides to the upper breast. The flanks are barred black and white, and the undertail is white with some darker streaks. The long bill and the iris are red, and the legs are flesh-brown. The sexes are similar; although the female averages slightly smaller than the male, with a more slender bill, determining sex through measurements alone is unreliable.

It sounds like this
Recording by Jérémy Simar from Xeno canto