Holographic Rooms are basically areas of Sirian City or the Fleet Ships that are comprised of physical objects manifested by energy. They feel and seem completely real. Holographic rooms can generate any setting including water to a limited degree depending on the number of people in the room. Unless overridden by someone high up in command, they are protected by a safety system preventing any and all permanent physical hard. For training purposes, holographic rooms can simulate injuries.
On the Extravia and Kalvania there are two holographic rooms on each ship for the crew to use. The Extravia's are larger and capable of more processing power, and interactive environments. However, there are still limits to what can be created, such as Gargorians have tried to replicate their home planet, but the rooms turn off as their safety settings kick in due to power concerns, overheating issues and processing ability.
That being said, beaches, lakes, mountains, snow and thunderstorms have all successful been replicated and experienced. As well as Unlife for combat testing. Though, many people use the holo-rooms for meetings, or as a means to escape.
Each Holo-room does have a standard set of pre-set environments, features, and a save feature, for environments to be stored without having to program them again. One can choose to leave their saved room in the holo-room terminal or for privacy, save it to their datapad.
As with the Gargorian Home World example above, the holo-rooms have issues replicating large groups or people, or variety of animals. Many users don't enjoy the choppy or video game style in which humanoids or creatures come out seeming, which may be a programming issue. Though, the processing power to replicate moving humanoids versus a a static setting is a struggle that programmers have had for some time.