Scuba Diving Computers – While Scuba Diving with Your Buddy: Can You Share a Single Dive Computer or Do You Both Need One?

It’s a no-no. You each need your own computer.

Nothing wrong with using both as long as you both have, and understand, how to use both. Whoever has the computer should have at least a set of tables as back-up anyway. Just follow whatever method(almost invariably the tables) is the most conservative. When I dive with a buddy my computers are always set overly conservative(I was bent twice due to a pfo so I need to be careful of any residual damage seeding naughty bubbles),so it’s pretty much just the same thing inasmuch as we’re both diving off differing no-stop/deco schedules.

It’s not ideal, but the very fact you’re asking the question kinda means you know that already.

There’s a problem doing this. Suppose you and your buddy are temporarily separated and they pop an additional 10 feet deeper for a bit. Your dive profiles are no longer the same. What the computer tells you is now only valid for the diver wearing the computer. The other diver is on their own and had better be keeping track of their profile during the entire dive and have their tables with them.
If on the other hand…your buddy is glued to you at the hip you can get away with it but is that still manageable risk? That’s where this becomes your call. There’s pros and cons either way. I prefer that both divers have a computer simply because that certainly is safer and Murphy and his law always seem to target the unprepared. It just adds a bit more expense for you. For myself it’s worth that expense.