“See, bad things happen to me on field trips. Like at my fifth-grade school, when we went to the Saratoga battlefield, I had this accident with a Revolutionary War cannon. I wasn't aiming for the school bus, but of course I got expelled anyway. And before that, at my fourth-grade school, when we took a behind-the-scenes tour of the Marine World shark pool, I sort of hit the wrong lever on the catwalk and our class took an unplanned swim. And the time before that...Well, you get the idea.” 

This passage shows how Percy’s demigod nature has affected him for much of his life. The cannon incident occurred because his battle instincts kicked in, and the aquarium relates to him being Poseidon’s son. These lines also foreshadow how Percy’s quest will affect the human world. His quest is like the ultimate field trip (with bigger consequences), and bad things happen on the quest, only on a larger scale than the mishaps from his past. The individual events are mirrored in later chapters. Percy both blows up a bus and takes an unplanned swim as a result of fighting monsters.

“I don't have any memories of him, just this sort of warm glow, maybe the barest trace of his smile. My mom doesn't like to talk about him because it makes her sad. She has no pictures.” 

While at the beach with his mother, Percy asks her about his father and, as always, gets little information. Percy’s mother has her secrets, and her unwillingness to discuss Poseidon shows how parents keep secrets from their children, especially when they believe keeping those secrets protects them. The lack of pictures of Poseidon implies two things. First, it’s possible gods cannot be captured on camera. Second, Percy’s mother kept no likeness of Poseidon because she wanted to live her life independently, and a god could offer her too much that would keep her life from being her own.