Deliberate mistake: The Messerschmitts have painted yellow fronts, this wasn't done by the Germans until after Dunkirk. Christopher Nolan has admitted doing this deliberately so the audience could tell the difference between the Spitfire and the Messerschmitt during the combat scenes.
Continuity mistake: As the lone Spitfire trails and attacks the German bomber, he hits the right engine, which starts smoking but the trail quickly fades. He then hits the left, which smokes a lot. We then see the same attack from below, and from this angle the both engines are smoking equally badly.
Answer: After running out of fuel, he kept his craft aloft as long as he could so he could shoot down the enemy plane. He then landed when and where he safely could, which was on the beach but in enemy territory. Ditching a plane in water is dangerous and would have meant far less chance of survival.
raywest ★