Not Known 3715:

This wreck is/was located in Alexandria's Eastern Harbor at a place commonly referred to as "Cleopatra's Palace". However, there is no solid proof to date that Cleopatra ever really resided there. This vessel was discovered by the team of Franck Goddio during excavation of the complex's inner harbor. The wooden vessel was fairly complete and contained a few artifacts that are normally associated with seafaring life aboard ship. However, due to the absence of most of the shipboard implements, this indicated that there was plenty of warning concerning the subsidence of the palace complex. The hull had a hole in it which would seem to indicate a collision within the harbor, possibly with a quay wall. Additional artifacts have been excavated from the area including sphinxes and statuary. Excavation of the area is ongoing.
For Divers:

Because the palace complex is located inside the Eastern Harbor, visibility is typically poor, ranging from near-zero to about 10 meters depending on the weather. The water typically is dirty brown due to pollution from the adjacent Western Harbor which is the maritime industrial port of Alexandria. Maximum depth of the palace complex is only 4-6 meters. There are still some items to see which have not been removed by the excavating archaeologists (Amphorae, a few column sections, a wine press, and a wall section. There is also a WWII era Italian airplane located near the area where Marc Antony's private sanctuary was located.
References:

Franck Goddio website

Personal diving experience :-]
ankh
Cleopatras Palace
Cleopatras Palace
Cleopatras Palace
Shipwrecks of Egypt Custom Products