Dominica is quite rightly famous for its waterfalls and there are plenty to go and see.

A good starting point is Emerald Pool - which is best avoided on days when the cruise ships are in as it can be busy then. It's a short walk and easy to get to and quite pretty - although not as dramatic as the others. You don't need a guide or anything - just pay at the entrance and make your way there.

Trafalgar falls is also another good one to go and visit - it is also an official tourist site so you need to pay to get in but you don't need a guide. There are two falls and one has a "hot spring" and it's really stunning to see both cold and hot rock pools.  There is a viewing platform which is a straightforward walk but try walking down to the falls themselves if you are able to clamber over a few rocks. Several guide books recommend getting a guide but it's really not necessary - it's not that far and you can see the falls for most of it so you know where you are going. You can either just stand at the bottom or climb up to the rock pool which has ice cold clear water - so do bring your swimsuit for a dip! Especially as it can be hot and humid getting there so diving into cold pool is most welcome.

Day Trips: when you want to do day trips, Calibishie Lodges arange them also. The service is good a find and the prices are reasonable.
Nigel is a very good tourguide.