In Aquaman, after defeating Black Manta in Italy, Arthur and Mera use a boat to travel to the Missing Kingdom. Presumably, Mera uses her power of controlling the water to drive the boat as there is no one else. My question is, why did they need a boat if both of them - with their Atlantic abilities - can swim much faster underwater than Mera can push the boat with her power?
At that time Arthur was wounded by Black Manta and lost consciousness.
Even Mera was exhausted due to the fight, She cannot carry Arthur and swim. Hence they used boat.
Mera : Arthur! Stay with me. Wake up.
Arthur : You steal the ship. Boats in the harbor is not public.