i'm banned from hoi4 forum so i can't answer on the thread,
But you could maybe try using paratrooper instead, and make them capture a port and then move your army there.

i don't really know how the navy work so i don't know if you have a way to get naval superioty faster but if you are ok with cheating you can tag switch as your ennemy and delete his fleet, or for exemple use the command tp, to teleport your troops where you wanted to naval invade