You can't feel or see it much when you're just floating in the water. It's like the phenomenon of a complete lack of wind while riding in a hot air balloon: You're immersed in the fluid which is moving, so you feel no relative motion.

You can feel it easily if you can touch or swim down to the bottom. Also, it's often possible to see where the sand bars and reefs that are next to the rip are located either by seeing the color of the ocean floor or by seeing the waves breaking; get behind those and you'll be out of the rip.