Well if we go by your standards, we will not be able to:
1) Drink onboard because the mixed drinks can get us drunk and we can fall overboard and kill ourselves.
2) We won't be able to swim because we might hit our head and drown
3) We won't be able to walk on the track because the wind migh get gusty and blowus overboard
4) We won't be able to gamble because we might loose our life savings and jump overboard
6) We can not drive (or fly) to the pier because we may have an accident and die
Oh by the way, I am one of those fat people you talk about, but I am a healthy person, no medical problems, and I don't eat that much, but I do try everything I can on a cruise because it may be the only time I get a chance to have something like that.
Bottom line, Drugs are dangerous and against the law. Get caught and take your chances with whatevery country you happen to be charged in. Like the CD on my last cruise said, don't be stupid, get your friend help and get their life on the right track. The customs officials will find it and you will be charged. (I added the your friend part).
Good luck and have a safe cruise.