Don't drink the water. This is one place where local water can be very dangerous. Samoa has a parasite that is unique to Samoa and if you have not developed any immunity to it, you will end up with severe chronic diarehea that will last months or even years. It is not that common but there are other hazards in the water as well so don't gargle in the shower or brush your teeth.
If you do get unlucky enough to end up with the parasite doctors in the US or other developed countries except perhaps NZ will not recognise what it is. It is just too specific to Samoa and too rare. Tonga has a similar parisite apparently as well.
The cure is simple. Six times the normal dose of Combantram does the job but don't do this without getting a doctor's advice. In fact if you tell a doctor about the Samoan Parasite he/she can then look it up and will then know what to do.
If driiving in Samoa watch out for Pigs. They are everywhere. If you hit one, do not stop but drive to the Police and report it. It is not safe to get involved with natives to apologise for hitting one of their pigs. They get a little upset.