Optimising a three-dimensional foil is becoming an essential part of the design process of high-performance sailing vessels. With the advent of foiling in the America’s Cup in 2013 and the subsequent interest in foiling, the Olympic committee decided that the NACRA 17, a high-performance catamaran already present in the 2016 Rio Olympics, was to start foiling for the 2020 Tokyo Olympic Games. The objective of this research is to explore the hydrodynamic performance variations of the NACRA 17 Z-foil by means of Computational Fluid Dynamics (CFD) simulations, analysing in detail the current design and the possible improvements that could be made to achieve a better performing boat. Exploring changes in the three-dimensional design leads to the understanding that small foil modifications provide similar or higher performances than the current design without affecting the functional requirements of the NACRA 17 class such as the general deck layout. Because small local changes in foil shape could have a large effect on performance, foil design optimization is especially effective for large numbers of shape variables [1]. Despite considerable research on aerodynamic and hydrodynamic shape optimization, there is no standard benchmark problem allowing researchers to compare results. The presented research addresses this issue by running a series of CFD simulations in order to compare the performances of different three-dimensional shapes and configuration arrangements.