Usually rips are only 10m wide. At special locations in the middle of a sandy beach, you can calculate, if you know the trick and angles.
As surfer we call them lift. They take you out for free, and then it's easy to step out, just as on a lift. But to a swimmer who has no idea they are usually deadly.
You can focus on some constant points, like the surf or some rocks, but usually it's easy to step out, and you feel it immediately.
I've never been in that situation. I think I seen recommendations where you should swim diagonally toward the shore rather than parallel, maybe that's the logic there. The thing is that there is an current toward the shore on either side of a rip, maybe you can sense the change in pull? Rips only go out so far before the water recirculates back to shore.
The pull is pretty strong, and you can feel it pulling you out. When it's not pulling at you any more you can feel it. You can be quite a long way offshore before you're out of it.
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.
But how do you know when are out of the rip, so you'd know when to stop swimming parallel?