Factual error: When Ack Ack is collecting shells on the beach for his father, he's really collecting shell casings... which should be where the guns are fired, not where the explosions are.
Continuity mistake: When Hoops is drawing a picture for Cassandra on the beach, he is standing facing the boat he is drawing on. When he helps Cassandra off the boat, he turns around. They talk briefly and as Cassandra is walking away, Hoops is unable to move cause he has sunk into the sand. He wasn't standing facing away from the boat long enough to sink that far into the sand.