The narrow navigable channel of the Upper Clyde passes close to the townships of Port Glasgow and Greenock to reach the Tail of the Bank where the river opens into a wide, sheltered anchorage. From here the river flows west, past Greenock and Gourock to the Cloch Lighthouse and then south towards Inverkip. In this short, six mile stretch of water and the adjoining sea lochs - Gareloch, Loch Long, Loch Goil and the Holy Loch - dozens of ships of varying sizes, from the 5000 ton Captayannis to small lighters and steam yachts, have met with disaster. The causes of their loss vary from bad weather, through enemy action to simple human error, but by far the most common cause of loss was collision. In its heyday, this small area of enclosed water was alive with passenger steamers, cargo ships and sailing ships of all shapes and sizes. The volume of traffic, and often the attendant cavalier actions of some of the river's captains and owners, inevitably resulted in many collisions. Often the damage was slight and only served to foster the romantic tales of the steamer trade on the Clyde but, tragically, a number of these incidents resulted in the loss of the ships and often the lives of many of the passengers and crew. This section of the Clyde has become one of the most popular dive destinations in Scotland. While it does not have the density of shipwrecks or underwater visibility of say Scapa Flow or the Forth, it is still able to offer an excellent days diving on large, substantially intact wrecks close to the central belt of Scotland. The depth of water and the shelter provided by the hills surrounding the anchorage, plus the fact that many of the sinkings have resulted from these collisions, mean that a substantial number of the wrecks are still relatively intact and therefore, very interesting for the sub aqua diver. Also a good number have landed on an even keel leaving the wrecks shiplike and easy to explore. They also attract many fish and are therefore popular with local sea anglers. In general, diving is relatively easy as the shelter of the surrounding land masses protect the area from all but the most severe weather and tidal flows are fairly weak. The major dangers for the diver are the depth and the darkness of most of the wrecks. Most lie in around thirty metres and, even if visibility is good, it is almost always dark. Safe use of decompression tables or dive computer and a good torch are essential elements of diving here. Good boat cover and use of the 'A' flag are also vital as, although the Clyde is not as busy as it use to be, there is still a lot of river traffic. Boat access is surprisingly limited with best slip facilities at Largs, Inverkip Marina and Port Glasgow.