You’re on vacation in a tropical paradise. There’s music in the air and the umbrella drinks are flowing. You’ve got a dive in the morning but, hey, that’s tomorrow. One more round won’t hurt, right? Wrong.
Too much alcohol leads to dehydration — one of the leading preventable causes of decompression sickness. Remember, diving itself is already plenty dehydrating, as you’re breathing dry air and the diuresis (lots of peeing in the wetsuit) that you get from immersion. Adding to it with a hangover is just asking for trouble.