Newfoundlands are very loving, good tempered dogs. They are messy, at least mine is. Just earlier today when I let Clifford,( 6mos old, 80 pounds) in from outside, he got halfway through the house on my light colored carpeting before I realized he was covered in mud from digging in a flower pot outside. They do shed and drool a lot, so if you are not prepared for that it might not be the right dog.
I have a very small yard, it's not an issue, we take walks everyday. My Jack Russel needs far more exercise than the Newfoundland. They don't have to have a pool, but certainly find the water irresistable. Yesterday when we were out for a walk, I stopped to talk to friends, Clifford was playing in a puddle by us and then decided to just lay down in it.
I do love the breed, love their personality, their goofiness, their big sweet faces, but they are expensive to buy and take care of and yes, they can be messy.