What is the most adaptable dog breed ?

What is the most adaptable dog breed ? Often on the weekends and in summer I'd like to take a dog for long walks , while in the weekdays shorter ones as I'm more busy. I'd also like a dog that likes the water as I live near the ocean and in summer it is warm enough to swim in. I'd love a dog that can come swimming with me. I'd also like a dog that can dog for long walks from walking on flat field , to walking up and around mountains terrain as I live in a mountainous area . I'd like a relatively healthy dog with a good lifespan . Having a that could walk far on weekends and not as much in weekdays would be perfect for me. I'd also appreciate it if the dog looks nice.