It's simple, it's crazy and it's funny as hell. Why? It's easy to understand. Show relies on general "randomness n craziness" and fast paced, dynamical interaction between characters as a main fuel for humor.
The show is made up of 13 minute episodes, and this short length is definitely a good thing; it means that the pacing is fast and concise, which is perfect for the humour used. Additionally it means that the show cannot string out jokes so that they become dull and monotonous. With reduced time slot, there is only an opening, which is catchy, energetic, and crazy.
Also, there will be many people who will not agree with the humour at all, in which case the show will be torturous to watch. After watching the first episode I would strongly recommend dropping it if you did not like what you saw, because it'll only be more of the same style of humour. For most people though this will not be a problem, since the zany humour is incredibly accessible.
Overall, Muromi on the Shore is a show that will keep you well entertained, having some incredibly funny moments that will catch you off guard. However since it isn't good enough to keep you laughing consistently, the show, whilst being entertaining, is nothing more than that. It may be a forgettable anime, but for what it's worth it provided me with a great couple of hours of amusement.