One of the major difficulties in the design of a wave energy device is the occasional occurrence of severe conditions at sea. The largest waves far exceed typical amplitudes over the year. Although it would be possible to make devices large enough to capture the power efficiently in these conditions, it is almost certainly not economical to do so. Survival of the device in these conditions is, however, essential. There are essentially two choices; give the device enough freedom to move with a large wave thereby limiting the force on the device or limit the possible movement while sustaining large forces. Either alternative means that at least an order of magnitude greater force or movement must be accommodated in the design just for survival. An approach that lies somewhere in between these two extremes is also possible. The best approach to take depends on type of device, its configuration and the power takeoff scheme used.