Your body turns off. You know that feeling of seasickness? You don't have to have ever gotten sea-sick to understand that because your sense of balance becomes disconnected from your vision going up and down, your body starts to get wobbly. Even if you don't get sick, you still feel wobbly when you step on land. Well SP is when ALL of your senses get disconnected. That can feel like a super exaggerated seasickness-like-motion. But normally it happens so quickly, you don't even notice.