Witte Leeuw
The Witte Leeuw, or "White Lion," a 16th century sail ship, is about 35 meters below the surface. (Learn more about its intriguing history by clicking here.) The ship has broken down somewhat over the years, but the ribs of the ship, as well as the canons carried by the vessel, are frequently visible.
The aquatic life isn't as abundant as it is at the other wrecks mentioned, but a particular highlight is that the well-known Jaques Questoe dived this wreck several times during his visits to the island in the 1970s. This expedition retrieved one of the bronze cannons, which is now housed at the St Helena Museum at the bottom of Jacob's Ladder.
Witte Leeuw has a 1604 date of manufacture on it. On the Diving page in Wikipedia, you can read about the cannon's recovery. The 1,311 diamonds, on the other hand, have yet to be found. They would have been kept in the stern portion, near the powder room, for safekeeping.
The explosion would have dispersed them extensively, and because diamonds are carbon and not metallic, they are nearly difficult to retrieve under 400 years of silt. However, if you go diving on or near the Witte Leeuw and see anything glistening...