Is a Plunge pool the bottom of a pool?

This happens when the Jandy-valve is set to pull too much suction from the skimmer. The pump will also sound like it's choking because it's not getting enough water from just the vacuum. Try turning...

The suction side cleaner - pool vac - may have air entrapped inside the housing. Inverting it while still under water may work.

The wrinkles are there to provide for liner shrinkage over the years.

Yes they are, seeing the bottom of a dark bottomed pool is not difficult at all contrary to the opinions of some

Swimming pools can have many types of bottoms. Most are cement or dirt. So if its cement and bumpy its probably wearing and the same if its dirt. When the pool was put in on top of the dirt is sand...