Display MoreShort Answer, Yes.
If your army unit(s) are at sea, they do 1/3 damage and have 1/3 strength. When disembarking, they are considered to be at sea for this purpose.
This is also at game start, Islands are very hard to invade.
It would not slow down disembarking even if they are attacked. Think of D-day Normandy. Allies got bombed but they still got on the shore.
Thanks for the help. If I still face any issues. I will update you soon.