“Moonpools” are open water-filled pools occurring in several vessels which exhibit very complex dynamic behaviour. And due to its size their dynamics can also effect the ship/platform behaviour where it exists. It is therefore an important and also complex problem to tackle in CFD: viscous-effects, low to high Reynolds number, moving structures, free-surface effects, wave effects, instabilities have all their role in moonpool analysis. A lot of work (non-public yet) has been done on Moonpools in the last years within Joint-Industry-Projects (JIPs), see http://www.marin.nl/web/JIPs-Networks/JIPs-public/Moonpool.htm. Anyhow, an example of typical ReFRESCO analysis on a fictitiuous moonpool+ship structure under incoming waves can be seen below.