Analysis: The Thief of Always
At one point Harvey wishes for a miniature Noah's ark, a relic from his childhood, and House promptly gives him an exact, flawless copy. The ark symbolizes Harvey's childhood. Harvey goes to Hood House seeking to extend it, shirking the responsibilities and sometimes painful experiences that come with growing up. Hood appears to give him what he wants, a perfect childhood without pain, worries, or hard work. Indeed, Hood's version of childhood is even superior to Harvey's actual childhood in many ways, due to Hood's magic not being restrained by the rules of reality.
Harvey's curiosity leads him to the lake, where he discovers creepy-looking fish ( actually Hood's past victims
) and loses his ark to its dark, gloomy waters. This event represents Harvey losing his childhood, he is forced to "grow up". Curiosity leads to knowledge—unpleasant knowledge, in this case—which in turn leads to the loss of innocence. Hood's lake represents danger that Harvey will have to face again eventually.
Harvey does manage to save a few figurines from the lake, but as soon as he leaves Hood House they disintegrate. The last of Harvey's innocence disappears as he chooses to return to the real world. Hood's false childhood cannot exist in the real world.