This is a long exposure photograph. The lenght of the exposure allows the water to become nice and smooth. It also allows the clouds to smoth out as they move across the sky. These kinds of photographs are fun to do as well as being quite beautiful and different.
To do this photograph I used a very low ISO and am F22 aperature. This allowed me to get a 30 second exposure without the use of a neutral density filter. You must have you camers pn a good tripod . Consider also using a cable release or a time delayed shutter release.
For those wanting to know the camera settings: Canon 5DM3 ISO 50 30seconds F22 and a tripod