Gotta correct you on that Dessert Fox.
If a naval battle occurs in the sea zone prior to the amphibious assault, then you have the option of retreating your navy as per normal BEFORE any round of fire. This includes the transports involved.
If the naval battle is resolved and the land units are offloaded into the hostile territory, THEN they cannot be retreated and are forced to fight it out.
If you realize in time that your navy is not gonna last against the defending one in that sea zone before the amphibious assault can even go through, you don’t HAVE to sentence your entire navy (transports included) to now certain death. You declare an amphibious assault assuming that you can win the sea battle, but the sea battle itself can play out just like any other.