Let me give you one of the other things you can watch for today after the chick hatches.
At some point, one of the loons will probably take the leftover white membrane of the eggshell in its beak and carry it into the water. It will swim a little ways from the nest and dive. It places the remains of the eggshell on the bottom of the lake!
I am not sure. But I have seen it happen too many times for it to be just an 'accident'. My guess is that it removes as much from the nest as possible that might draw the attention of a seagull or an eagle or a crow.
It is just another one of those amazing things about loons. Watch for it.