Hello,
My logbooks are soaked and nearly ruined (as well as my macbook air

). If I get a new one, can I copy all of my old flights and copy my CFI's number and discard my old ones or should I keep onto my old ones "just in case"? I have pictures of my old logbooks, I just don't want, if I go into a job interview, for them to think it's fishy.
First off, you aren't the first person to have damaged logbooks and you won't be the last. Your goal is to now make a good faith attempt to document the training you received and the hours you have flown. Everyone knows that this will not be a perfect record, but as long as you are conservative and honest about your estimates it will be OK.
DO NOT sign your old CFI's number into your new replacement logbook. This could be considered forgery. If you do try to reconstruct your logbooks with dual received, then log it as such and note that the originals were destroyed in a house flood.
If you can make copies of what you have left then do so. Anything is better than your fuzzy recollection of how many hours you flew in May of 2008. If the old logbooks are not totally destroyed, then keep them in a safe place.
You can ask the FAA for copies of your most recent 8710. If the flight school you trained at or worked for you can try to dig up your records there.
Ultimately you will have to start a new logbook. Save the first page for entering estimates from the records that you can salvage. Once you have done that, then that is all you can do.