Inthat light, I'd reconsider not renting a dive computer. DMs will lead dive profiles based on what their computers will allow. If you don't have a computer, you have 2 options: 1) dive with tables and actually use them, which may annoy people if the shop's policy is the whole group ascends at once, or 2)you trust the DM's computer, which is common practice in some (a lot?) areas but not a good idea. If you rent a computer for your trip ($50 for a week is common around here), you can still plan your dive and be able to follow a similar profile to the DM, so you don't necessarily have to settle for shorter dives... how much is a few extra minutes of dive time per dive worth to you?