My proposal on that thread was the following:
The main feature of the flag are the shells. The pearl fishing on the islands is famous since Roman times and was once among the most importants of the world. Today, its relevance isn't the same, but it still exists (including as a touristic attraction, together with scuba diving). Having a pearl a generic circular flag, shells were chosen for more direct identification. The flag have four shells, as four are the inhabited islands of the archipelago.
The white color can also represent the white beach and the limpid waters of Dahlak. The red color is chosen as a reference to the Red Sea, and to the Islamism (islanders were converted yet on 7th century).
An alternative proposal have white circles (representing pearls) instead of white shells, making it simpler but more generic.
Your comments are very welcome.
Remembering you can access the Flags Forum thread here.