I've been thinking about this (stupid) chapter a bit. How does Snape know the approximate area to find Harry? Was he following Ron and his deluminator? Is he hiding in the bushes (reading a Girls of Alchemy magazine?) letting his doe-a-deer patronus prance around until it can lead Harry to a nearby ice-overed fishing hole (convenient, that)? Why put the real Sword underwater? Why not hang it in a tree? If Snape sincerely wanted to put the SoG (a proven Horcrux killer, btw) into Harry's hands why not do something that would assuredly work without giving away Snape's role? Like, tie it to a thestral or Buckbeak or even give it to Kreacher -- all Harry-friendly beings Snape could access.

They could have pranced and yoo-hooed around the forrest and Harry wouldn't have to dive naked into the water without a lifeguard present. Harry was able to accio the GoF in B4, so why not the SoG after breaking the ice? This chapter is so convoluted, it makes you wonder what happened to the very-clever Jo of B1-B6.