Commercial fishing is one of the most dangerous primary activities. Most of the 24000 yearly accidents identified by IMO are occurring on small vessels. The French SOS-Stabilité research project aims at better knowing and modelling dynamic stability issues occurring on small fishing vessels (12 to 24 m), prior to the development of solutions for improving their behaviour, through the evolution of the ship design and through the design of appropriate embedded systems. This pa-per presents the first part of the project: sea andmodel tests, development of a ship behaviour time-domain simulator (including fishing gear modelling capabilities) and first validation of this simula-tion tool.