It's satin and waterproof, but would it be okay to take for a dip in the pool? I wear ear plugs and would like something to cover them a bit better, and am just unsure if this cap is okay to full submerse.
Proper swim caps are usually made of rubber and cover the entire hairline like a theatrical bald cap, and are then held in place with a chin strap so no water can get to the hair - thus, it becomes just about airtight.
Elastic banding on a shower cap is not the same - it'll likely be pulled off by the drag of the water.
Definitely not. Have you ever worn sunglasses/eyeglasses into the pool and had them start to float up over your head? This would do the same thing, plus the chlorine would probably do major damage to it. You'd be better off purchasing an inexpensive swim cap.