This paper is concerned with the issue of the efficiency of sea wave energy conversion. It is shown that the efficiency increases significantly if a low-damped mechanical oscillator, which is adapted to a wave power spectrum, is used as a primary converter. Two major types of oscillators are considered. The pendulum-type converter is found to be the most promising. A new schematic of a pendulum-type converter is suggested and briefly described. The converter consists of two oscillators adjusted to work in resonance mode. The first one includes a ballast-controlled floating platform pitching on sea waves. The second oscillator is a long sector-shaped pendulum located on the floating platform. The use of sea wave energy converters is promising in regard to the widespread use of renewable sources and elimination of the environmental impact of fossil fuel consumption in coastal regions. Various systems have been developed and projects implemented in this field.