In this article, nonlinear dynamics tools are employed to quantify the ability of pendulum harvesters to recover energy from the sea waves. The versatility of pendulum harvesters is highlighted, as it is shown that devices can be scaled to produce usable energy from 6 W to 10 kW. Several aspects of the pendulum's dynamics having a key influence on power generation are discussed using bifurcation diagrams, parameter spaces, and basins of attraction. Parameter ranges that minimize the need for a control action are identified, and an explanation is provided on why tilting the pendulum's plane of rotation improves power generation. A practical mathematical model of the parametric pendulum is formulated for such a purpose. This model incorporates the possibility of accounting arbitrary number of concentric masses while allowing a simple and direct correlation between dimensionless approaches and the myriad possible physical configurations of the system.