Umm Rus is a sandy bay just south of Port Ghalib. It has a small reef on the northern side, which is okay but compared to the large reefs such as Elphinstone, it is a bit of a let down. The sandy bottom makes the visibility in the bay very poor, similar to UK conditions, 5 to 10m visibility. However, there is quite a lot of sea life living in the sandy itself, crabs, especially hermit crabs, stingrays and other bottom dwellers.
The reason to dive here is for the Dugong, or sea cow. They can often seen in the bay, a gentle creature that grazes on the sea grass munching away for a few minutes and then swimming along to its next site. The are quite easy to spot (follow the group of snorkellers on the surface). You can get very close to them when diving and they don't mind being filmed.