You'll find this tranquil and delightful restaurant near the Hilton at a kiosk around the edge of the river. They have very good quality dishes at a very reasonable price. And, its set on a beautiful location: Right at the edge of the river, on the beach, in this clean, neat, little town that is the gateway to the island of Borneo from the mainland of Malaysia. Definitely worth it.
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
Don't miss it. The Geographer café on the corner of Jonker Street. This is the cafe of Melaka tourism of excellence, and one can understand it. The prices are naturally a little cheaper in lesser known places, but they are soft, and most importantly, the food is tasty.