Check out this one: https://en.wikipedia.org/wiki/Valonia_ventricosa

The cytoplasm of those are very interesting. It has multiple partitions, and the cytoplasm is very viscous. They don't "pop" if there is damage or leak all their contents into the water. They can repair some amount of damage.

More even if the think that the structure is inside a fluid and subject to strong forces of pressure, currents and tides and bombed with sand each day. And we have a thin 1cm long cell that still somehow navigates it and don't break. It just does not feel right physically.

not to mention the cell that is a chicken egg

It is the yolk of an egg which is the single cell / ovum in birds.

And yes, if there's a larger cell than an ostrich yolk I'm not aware what it is.

Biologically, an eggshell isn't a cell wall.

ostrich egg?

Ostrich yolk technically