## 1 Introduction  
Ocean waves constitute an important source of renewable energy, and its high energy potential along the coastlines of the world has been calculated to be 2.11 TW (to 95% confidence) [1]. Nevertheless, efficient energy extraction from ocean waves remains a considerable challenge. Many technologies have been developed and several are still under investigation. However, apart from the usual problems common to all renewables (e.g., fluctuation of the output power or non-competitive prices in energy production [2, 3]), wave energy still faces several issues related to design optimization, the shapes and sizes of devices that attempt to harvest energy from an ever-changing and dynamic resource (intrinsic dynamics of the directional wave spectrum) [4, 5]. This means that specific wave energy converter (WEC) technologies are best suited to a given set of wave conditions. Therefore, the estimation of wave energy availability must take this intrinsic condition into account, unless a very flexible technology adapted to all possible wave types is developed. Some of the more well-known devices are point absorbers, oscillating water columns (OWCs), attenuators (e.g., Pelamis), and overtopping/terminators (e.g., Wave Dragon); however, only a few of them have actually been used to generate energy from waves in practice. An example of a device that was tested for a commercial phase is Pelamis Wave Power in Agucadoura, Portugal. This was the first commercial wave energy farm in the world commissioned in 2008 with 2.25 MW of power generation supplied by three Pelamis devices; however, it only operated for a brief period due to technical difficulties with some bearings [6; 7]. A second version of this device appeared in the UK in 2009, with 750 kW of power generation: the Pelamis P2 (from the Pelamis Wave company [7]) whose testing site was at the EMEC (European Marine Energy Centre) in the Orkney Islands, Scotland. Unfortunately, the company had financial difficulties in 2014 [8]. Another concept was Oyster 2, developed for Aquamarine Power, with a generation capacity of 800 kW; it was also installed and connected to the grid at the EMEC in June 2012. The test program ended in 2015 and the device is no longer in the water since the company ceased operations [9]. One other example is CETO devices, a submerged point absorber installed in 2010 in Frematle, Australia, connected to the grid in 2015, with some of the excess energy production going into desalinating seawater. The commercial-scale CETO 6 unit commenced in 2017 with a 20 MW system, which could be expanded to 100 MW [10]. At present, these systems are being tested in Europe [11]. These cumulative experiences have been used to improve WEC technology and optimize the system's performance. Notwithstanding, this kind of energy system is generally complex and expensive, with a relatively high cost of operation and maintenance [12]. Within the aspects that need to be considered in the performance of a WEC are the local environment and device characteristics, as well as the effect of other devices if we consider a wave energy farm [13]. It is also important to take into account the full cycle of the devices, from construction to the decommissioning and recycling of the parts, including its environmental impacts [14; 15]. The complexity of wave energy technologies often goes hand in hand with their manufacturing and maintenance costs; therefore, a simple, tested, and optimized design could minimize costs and become commercially feasible [16]. One of the most important components that determine the energy harvesting efficiency of a point absorption device is the design of a buoy [17]. The buoy captures wave energy from the ocean and transfers this energy (by means of a power take-off mechanism) to a generator to be converted into electrical energy. The movement of the buoy is induced by the free surface waves and the maximum power absorption is attained when the point absorber is in resonance with the waves [18].