“It's our shadow!—the shadow of the Dawn Treader" said Lucy. "Our shadow running along on the bottom of the sea. That time when it got bigger it went over a hill. But in that case the water must be clearer than I thought! Good gracious, I must be seeing the bottom of the sea; fathoms and fathoms down." [...] At present, for instance, they were passing over a mass of soft purply green with a broad, winding strip of pale grey in the middle of it. But now that she knew it was on the bottom she saw it much better. She could see that bits of the dark stuff were much higher than other bits and were waving gently. "Just like trees in a wind," said Lucy. "And I do believe that's what they are. It's a submarine forest.” FairyKelpSubmarine Forest Book:The voyage of the Dawn Treader Source: The voyage of the Dawn Treader