Apart from the wind and the solar energy, the ocean energy is a promising and predictable alternative source of energy. This green energy from the ocean is inexhaustible and in the past few decades, extensive research has been carried out to convert the ocean energy into electric energy. The possibility of using the direct drive linear generators (LG) provide an opportunity to harness the clean electric energy from the oceanic waves, without the need for intermediate mechanical conversions. In this chapter, advanced modelling approaches for designing permanent magnet linear generators (PMLGs) are discussed and a four-sided rectangular permanent magnet LG (4SRPMLG) is proposed to increase the output power. As the cost of most of the permanent magnet (PM) machines primarily depends upon the cost of the PMs, the paper shows that with the same amount of PM material, the power output of the 4SRPMLG can be greatly increased when compared with that from the conventional 2SRPMLG. Thus, the 4SRPMLG can produce more power with a slight increase in cost. Initially, the paper presents the analysis of a conventional 2SRPMLG using the optimized design parameters obtained from the Ansoft/Maxwell simulation software and the results are compared with those from the existing literature. Then, a 4SRPMLG, with the same size and the same material of the translator of the 2SRPMLG, is designed. The simulation results show that additional power can be obtained with only the additional cost of the added copper and iron in the stator. A three-dimensional transient analysis is performed instead of the traditional two-dimensional analysis to provide a higher degree of confidence in the obtained results.