You need a valid passport and proof of a return ticket to enter Dominica, unless you are a Canadian citizen, in which case you simply need a birth certificate and a valid form of ID. Check with the US Department of State for more information. Nationals of America, the UK, Canada, and Commonwealth countries do not need visas for stays up to 21 days. Extensions may be granted by the Dominica consulate.
Health and Safety
Dominica is one of the safest islands in the Caribbean, with low crime rates, but you still need to take the usual precautions - better safe than sorry. No poisonous insects or snakes live on Dominica. Tap water is generally ok to drink, especially in the cities and large towns, but it may have a slight chlorinated taste. If you don't like the flavor, you can easily buy bottled water, which is readily available everywhere. You can safely drink milk or consume dairy products because they are pasteurized. It is also fine to eat washed vegetables and fruit, as well as well-cooked seafood, poultry and meat.
Wear protective clothing and bug spray, especially when in the forests. Keep your doors and windows closed at dawn and dusk to prevent mosquitoes from entering. Vaccinations against tuberculosis and hepatitis B are recommended.