The photosphere (the visible surface) of the Sun is like
a) the surface of Earth; you could stand on it, if you could survive the heat.
b) the surface of the ocean; you couldn't stand on it, but you would clearly be able to detect differences above and below it.
c) an apparent surface; you would notice very little change as you go through it, as when you fly through a cloud.
d) the surface of a trampoline; you could land on it, but the intense pressure would push you away again.
Answer: c) an apparent surface; you would notice very little change as you go through it, as when you fly through a cloud.
The visible light we see comes from the photosphere - creating the appearance of a sharp edge, or surface, to the Sun.