The invention relates to a wave-power unit for the production of electric power. It comprises a floating body (1) arranged for floating on the sea and an electric linear generator (2) having a stator (5) and a translator (8) reciprocating along a center axis. The stator (5) is arranged to be anchored in the bed of the sea and the translator (8) is connected to the floating body (1) by connection means (3, 7). According to the invention the generator (2) is enclosed in a water-tight encapsulation (4) having an upper end wall with an opening through which the connection means (7) extends. The opening has a seal (12) that seals against the connection means (7). The seal (12) is flexibly mounted. The invention also relates to the use of the wave-power unit and to a method for producing electric power.