WRECKTOUR:137 The Castlereagh

IT MAY HAVE STARTED LIFE as the Firth Fisher, but it was not a fishing boat but a 443-ton coaster of the classical layout, with two holds forward and engine and boiler aft.
We begin at the back of the second hold, where a bulkhead (1) separates it from the bunker space. This is where skipper Martin Jones' shot had caught when I last dived the Castlereagh and sketched the wreck.
Orientation is straightforward, with the bow just east of north. The dive usually begins while the tide is still just about running before truly slack water, to either the east on a flood or west on an ebb.
On a high-water slack, the bow is to the right as a diver reaches the bottom of the line, or to the left on a low-water slack. The depth will be 33m on a high-water slack, or a few metres shallower on low water.
A second indication of direction is that the port side of the aft hold has fallen outward (2).
What little remains of the deck has collapsed to the seabed, leaving the broken outline of the hatch coaming just out of the sand.
Continuing forward, between the holds is an intact area of steel deck, with pairs of bollards to either side and a cargo-winch (3) in the middle.
The position of the wheelhouse varied between two locations on coasters of this size - aft of the holds, above the bunker space and boiler; or, despite the machinery being located aft, between the two holds and therefore just forward of amidships.
The aft location was generally, but not always, favoured on later ships. A between-the-holds location was more traditional, and photographs show that the Castlereagh followed this pattern.
On our tour, all the structure of the wheelhouse has decayed, but the helm (4) still lies on the deck between the holds, just forward of the cargo-winch.
Crossing the forward hold, another cargo-winch (5) is solidly attached to the deck forward of the hold, just aft of the bulkhead separating it from the forepeak.
The deck at the bow has been ripped off to starboard, leaving a pile of anchor-chain (6) visible in the bottom of the bow, where the chain-locker would have been located.
Outside the hull on the port side, what looks like a domed water-tank (7) is trapped between the bow and the seabed. This is an unusual place to find equipment normally located close to the engine and boiler, and evidence of commercial salvage in the past.
On the other hand, this object may have nothing to do with the wreck, and simply have been trapped by the tide.
Rounding the bow, a scour in the soft rock of the seabed adds a metre or so to the depth. One of the Castlereagh's anchors (8) rests on the seabed just back on the starboard side of the bow.
I would describe the bow deck as having been ripped off to starboard, because that's the only way it could have been peeled and turned upside-down, with a pile of anchor-chain in the middle of it.
Normal decay of an initially intact wreck could not have resulted in the deck being turned over before falling. Perhaps this was collateral damage from an old "smash and grab" salvage of the coal cargo, or perhaps a sizeable ship once fouled its anchor.
The Castlereagh's anchor-winch (9) lies upside-down beside the inverted bow deck.
Returning aft along the starboard side of the wreck, the decay of the forward hold is opposite to that of the aft hold we have just crossed, with the port side more intact, and the starboard side fallen outward (10).
Back past the shotline and the bunker bulkhead, the bunker space (11) still contains a few scraps of coal. The footing for a mast has fallen to the bottom of this space, forward against the bulkhead.
Next we come to a single large boiler (12) that spans the width of the hull, separated from the engine-room by another bulkhead (13), which has fallen forward to rest against the boiler.
The engine (14) is a straightforward two-cylinder compound unit, often preferred on small coasters to the more efficient, but bigger, triple-expansion engine. Aft of the engine, a set of steps leads from the engine-room to the missing deck above.
Now at the stern, the deck still shows the outline and a few upright supports (15) from a cabin. The usual pairs of bollards are still firmly attached to either side.
Dropping over the side of the wreck again, the scour at the stern is considerably deeper, descending to 37m on a high-water slack.
Most of the propeller has been salvaged, with a single blade (16) remaining in the bottom of the scour. Next to it is what looks like part of a pump from the engine-room.
The rudder has been torn away, I would guess in the course of salvaging the rest of the propeller.
The steering was a simple tiller (17), pulled from side to side by chains or cables, now twisted by almost 180° to point out from the stern.
Which brings us to the end of our tour. Unless you stop to rummage or take photographs it won't be a long dive, so is ideal for those not wanting to get into too much decompression.
To ascend, local skippers generally prefer divers to use a delayed SMB.
After slack, the tide picks up fiercely, and a shotline with divers hanging on it usually gets pulled under.

Thanks to Martin and Bryan Jones.

DEPTH -20m 20m-35m 35m-45m 45m+ DIFFICULTY RATING