This one is glaringly obvious, but skin cancer is the least metal way to die. Also, sunburns are for amateurs, and you probably paid money for those tattoos, why not protect them?
Another obvious choice, but let's be real: You probably don't even know what state he or she is from, and it's going to be really rough explaining to your future offspring that they were conceived in international waters between Napalm Death and Mayhem's sets. Also, the clap.
Diarrhea at sea ain't no joke, especially when you've dropped major coin to party with your favorite bands! So sidestep the cruise grub plague with a bit of precaution. Also, what could possibly more metal than pills that are actually teeming with (healthy) bacteria? Nothing.