A basic synopsis of the underwater fight is as follows:
The ship sets sail toward the east and an apparently larger sun shines before them. While looking overboard at a perfectly calm, clear sea, Lucy notices that there are shapes that look rather like a road and forest under the water. It is not long before she sees a large, underwater castle and sea people. The sea people, who are on a hunting expedition, spot the Dawn Treader and move closer to investigate. One of the sea people, who looks like a king, shakes his spear at Lucy in a menacing way. Just then, Edmund and Drinian come up behind her. She shows them the sea people. Drinian instructs them to turn around and not to look. It wouldn't do to have one of the crew fall in love with a sea person or underwater world. As he tells them this, a man overboard is sounded. The "man" is Reepicheep who was provoked to fight the sea-king. When Drinian pulled Reepicheep on board, he insisted that he stay quiet about what he had seen. However, Reepicheep was excited about something else entirely. The water was fresh. Reepicheep repeats an old rhyme he heard while in his cradle about the waves growing sweet at the utter east. All members of the ships company drink the water, which gives them more tolerance for the increasing intensity of the sunlight. It also makes them less desiring of food or sleep.
Now the question is, will the scene be played out. Obviously to some extent - but one would hope that we don't have to see a huge fight in the water with mermen and maids...
I'm a purist. What can I say?