It is ironic that Huck is sleeping like a dead person, because everyone else believes he is dead.  

Huck considers himself to be a robber and it could have been him on the boat.  It shows that Huck has some sense of morality, but it only shows when he has time to think about it.

Huck is still an adventurous thirteen year old boy.  He wants to go on adventures and not think about whether people were coming for Jim.  It also shows that Huck does  not understand the severity of Jim's situation.  Huck does not understand that every thing they do out in the open