Siyul is the name for two islands that lie about a 20 minute boat ride south-west of Abu Nuhas. The larger island (about 600m across) is surrounded by a about 2 km reef (east to west).
The dive boats tend to pull up near the beach on the south side of the island (if you plan it right - it is also a fantastic place to have a BBQ on the beach).
In 2008, we spend 3 days diving this site - litter picking duty - and we were surprised on the amount of rubbish we were able to pick up (including engine oil filters) - after covering the front boat deck with black bin liners, we also spend a bit of time exploring the various elements of this reef.
The reef is relatively shallow and drops away from about 8 metres to about 25 metres in south and 30 metres in the west. There are a some lovely rock outcrops and pinnacles just to the west of the island, and a lot of soft coral a bit further out. The soft coral is home to some leopard sharks - which are easily scared off and missed.
On the South Side there, at approx. 37 metres, there is a coral cave (about 10 metres deep). Supposedly, a leopard shark makes it his home (well he wasn't in the couple of times we visited). The reef drops of quite sharply along the edges and there can be quite a strong current pulling along the south west end of the island. By keeping close to the wall, you are able to keep nearly still by swimming into the current, otherwise it is quite a fast trip into the Red Sea and the deep blue.
Diving along the South Side wall does offer depth and by floating with your back against the wall, you have a reasonable change of meeting and seeing some larger fish passing between the two Siyul islands. We have been able to spot dolphins, trevally and yellow fin tuna.