The semi-closed flexible fish cage (SCFFC) is a new concept that is supposed to be an alternative to conventional net cages as an important part of the next-generation aquaculture system. In this study, the dynamic responses and sloshing of SCFFC in regular waves are studied by experiments. A 1:30 physical model is made and set with several accelerometers, wave gauges, and cameras in a water flume. Waves with different periods and heights are made, and the dynamic responses and water levels inside and outside SCFFC are measured. The surge, heave, and pitch of SCFFC increase as the period of the incident wave increases. Its dynamic responses are similar to that of a semi-closed rigid cage, but the magnitude of the motions is much smaller. The bag is deformed and shows strong non-linear responses under some wave conditions, which should be attributed to the complex interactions between sloshing, wave field, and bag’s deformation. The filling level of inner water has a great influence on pitch, which might be attributed to the interactions between the moving inner water mass and deforming bag.
