but will air units still sink the transport if it is offshore?

What happens to transports during an amphibious assault if the attacker fails? Say there are no defending naval units and only land and air units are in the territory being invaded, do the transports just automatically die or do they remain offshore?
Or if there are no air units left, can the land units destroy the transport?

OK so me and my buddies are wondering the following questions about territories and sea zones:

1. Are territories and sea zones considered attached? eg Flying over Kwangtung and SZ 59, is it considered one move, or two moves, one through the sea zone and one for the territory?

2. Are naval units in sea zones adjacent to territories vulnerable to attack from air and land units in the same territory? eg Can German navy units pass through sea zone 6 without being attacked by air and land units from England?

3. Do air units count sea zones adjacent to territories as a move or as part of the territory? eg Does it take 2 moves to fly to western europe from eastern canada or 4 moves, counting the sea zones as separate territories?

Clarification would be greatly appreciated, thanks.