The vast majority of restaurants and nightlife in Dubai Marina is located near the Dubai International Marine Club end. However, make your way in the opposite direction toward the quieter Marina Beach area and you'll come across one of the best seafood restaurants I've eaten at in Dubai.
Aroos Al Bahar Seafood is run by friendly locals who understand the success of their restaurant is based not just on the food but also the service. They are attentive and even invite you to select your exact fish, prawns or lobster from the fresh catch display inside the restaurant.
Below: The restaurant has outside seating right on Dubai Marina. Go in the evening around sun set to get the best views.
When the food comes out you'll be just as happy as you were with the service. I had Sole, Tiger Prawns, rice and salad, all for a reasonable 100 AED ($27 USD). The prawns and sole were fresh caught and the chef didn't overwhelm you with seasonings and sauces. Stick with having your fish grilled and I can promise you'll love it.
Below: Aroos Al Bahar is located down the quieter end of the marina so it doesn't get the same amount of visitors as it should. But that's an advantage for you as there is always great outside waterfront seating availalbe!