Bismillah Restaurant is one of a number of Indian/Malaysian resaturants in Semporna. I loved having roti or indian dosai with cardamom spiced tea for breakfast there. Located on the main street with the dive center in Semporna, the Scuba Junkie, Bismillah also has a menu in English and offers free and pretty fast wi-fi connection.
The Mabul Cafe is the best restaurant in Semporna for its affordability and service. It serves Chinese, Malay and Western cuisine at good prices (3 euros per fish), as well as alcohol, something that most restaurants in Malaysia don't serve because it's an Islamic country. It's on the first floor of a building on the street that leads to the port, and it has a beautiful terrace for a great afternoon or night. A complete guide for Diving in Malaysian Borneo is at http://www.vagamundos.net/2011/pagina.php?id=12009
When I was in Semporna in 2006, the Scuba Junkie dive center had just opened a backpacking hostel in front. It has become greatly successful because if you dive with them, you only pay half price for accommodation. When I went back in 2011, I saw that they had completed the complex with a bar and restaurant on the ground floor with an international and diving flair. They certainly serve the best (perhaps the only) pizzas in Semporna. The prices are also pretty western, you'll pay 7 AC for a pizza. Complete guide to diving in Malaysian Borneo http://www.vagamundos.net/2011/pagina.php?id=12009