Fjord is a geologic feature caused by glaciation
The glaciated valley which forms the basis of a fjord exists because of the slow movements of glaciers during the ice age. The glaciers carved out typical u-shaped valleys in the Earth with their movements and sheer weight, pushing detritus to the mouth, where it would connect the ocean, if it was not filled with ice. A fjord tends to be deepest in the middle and the back of the valley, because this is where the glacier existed for the longest period of time, and the bottom of the fjord is well below sea level. Although some fjords take the form of an estuary, a mixing zone for salt and fresh water, most fjords are actually inlets of the ocean, and do not connect with rivers or streams, although they are quite long, and may stretch for miles into the interior of the land.
Although fjords may have existed in more locations at one time, they have been eroded by the actions of the weather over the centuries. The Western facing coastlines of nations with fjords, however, are abundantly littered with the striking ocean inlets. The steep slopes of a true fjord make it an unsuitable place to take people who do not know how to swim, as there are few shallow areas in which to learn swimming. However, for skilled swimmers, exploring the fjords in the summer can be a pleasant activity, and many Norwegian families take summertime trips to the fjord region for recreation. In addition, numerous tour companies offer fjord cruises and trips for people who want to see the fjords from the deck of a boat.