POSEIDON is structural design and analysis tool which was developed by Germanischer Lloyd (GL) more than two decades ago and has been continuously extending in functionality. A six-week trial version is available under www.gl-group.com. The initial motivation for POSEIDON was to accelerate the development and analysis of ship hull structures to ultimately speed up approval time for GL customers. Over time, the user base has widened and cases are known where structural design is based on POSEIDON even for ships eventually classed with other classification societies. POSEIDON has also become popular in academia for teaching and research, Salas et al. (2009).