Although river cruises and ocean cruises are alike in many ways, you will see some vital differences as well.
The ships for ocean cruises are typically bigger than those made for river cruises, and offer more comforts in the individual rooms. Therefore, they are able to hold significantly more travelers aboard. On river vessels, because there are not as many passengers, the feeling is more familiar and you have more opportunity to really get to know fellow travelers.
As opposed to ocean cruises, which are often traveling in open waters for days at a time, river cruises pretty much never sail a single full day at a time. Every day takes travelers to a new port of call. The sensation of visiting new places is also felt while the ship is cruising since the outside view is constantly changing. First-time passengers might want to start with a river cruise for several reasons including the destinations fact that land is always in sight, the water is shallower, and the sailing is smoother, so there is practically no chance of getting seasick.
That said, ocean cruises typically have more elegant benefits including gyms to work out, more of a selection for dining, and fantastic live shows. But river cruises are nice in that they feature inclusive pricing that covers water, alcoholic drinks, Wi-Fi, and even some fun tours off the ship.