NOVELTY - The device has a pulley (5) attached to a seabed (8), and a float (2) that is moved by energy of swell and/or waves (1) of sea. The float is connected to an end (3a) of a cable (3) traveling on the pulley under the effect of the swell and/or waves of the sea to rotate the pulley. The pulley is connected to an energy-harnessing system (4) i.e. water pump. A submerged float (9) is connected to another end (3b) of the cable. The pulley and another pulley (6) are fixed to the seabed by a concrete slab (7).    USE - Device i.e. wavepower system, for harnessing energy from swell and wave of sea into electric energy.    ADVANTAGE - The submerged float is connected to the end of the cable, thus allowing the device to be less bulky, cost-effective and simple, and allowing large part of the device to be immersed while avoiding the risk to fauna and marine flora. The submerged float maintains the cable to be permanently energized, and ensures the voltage in the cable even when the swell causes rapid lowering of another float that floats on the water surface, thus allowing optimal rotation of the pulley. The pulley is connected to the energy-harnessing system, thus providing optimal production of energy. The pulleys are fixed to the seabed by the concrete slab, thus ensuring stability of the device. The utilization of the pulleys ensures the balance state and rapid reaction by the submerged float. The device provides resistance to storm. The device automatically adapts to changes in water level, and effects of marine current and wind.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for transforming energy of swell and wave.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of an energy harnessing device with a pulley connected to an energy-harnessing system.    Swell and/or waves of sea (1)    Float (2)    Cable (3)    Ends of cable (3a, 3b)    Energy-harnessing system (4)    Pulleys (5, 6)    Concrete slab (7)    Seabed (8)    Submerged float (9)