Water is a vital element for human beings, its quality must be supervised through laboratory analysis and in-situ analysis with payload instrumentation in manned and unmanned vehicles. An unmanned surface vehicle, named EDSON-J, is under development since 2019 in Arequipa-Peru, presents a catamaran hull shape, and serves to monitor water quality in huge reservoirs, lakes and coastal waters. This paper deals with the vehicle hull shape design to find its main parameters and tests different slender body geometries to find polynomial representations for its main sections. The results are also validated using the Maxsurf computational tool and, experimentally, performing circular maneuvers.