Serenity wasn't supposed to make everyone immune to pressure sickness until after she had finished the sixth Labor. She didn't get every single person in the kingdom, but she had covered most that were going to be involved in the war tomorrow.
As Matt floated down with her, Serenity stirred, which made him relax a bit. If she was already returning to consciousness, then she would most likely be fine. As he reached the sea floor, Selena and Levi came swimming up to him with equally panicked expressions.
"What happened?! Where did you two go?! Was that Serenity's power just now?!" Selena asked as she frantically checked over Serenity.
"I'll explain everything once we get her to into a bed. She needs to eat and rest," Matt replied before swimming passed everyone in a beeline for the palace.