If you capsize a boat or if it capsizes, it turns upside down in the water. The sea got very rough and the boat capsized I didn't count on his capsizing the raft. = overturn. if a boat capsizes, or if you capsize it, it turns over in the water (Perhaps from capuzar , from cabo + chapuzar )
How upsetting (Leave the boat upside down until you either get it on shore or the rescuer takes overroll it back upright and you will fill it with water, making life difficult )