They are pretty soft, they're not hard like a chicken egg. Also amount of calcium in diet can play a role on thickness of shell. Extra calcium for a turtle that lays eggs is a good idea. That said also the egg probably absorbed some water but that is fine. Eggs laid in the water that have been in water for hours have been successfully hatched by people. Since the egg was put in the incubator do not ever touch it. Waiting is the hard part. Especially at the beginning. The embryo attachs to the side of the egg and the slightest turn of the egg can break it off and it will kill it.
There is one way to tell the egg is good. Usuaully with a day or two all the calcium from the shell heads towards the center of the egg where the embryo is. This is called "chalking" Usually it creates a white band around the egg or in my diamondback terrapin eggs i got a just a circle at one where calcium had disappeared from the area. So basically if egg changes color like white faded out at the ends of its most likely fertile.
Here is a Common musk turtle egg I hatched out a couple years ago "chalking"
