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Article #7

Title: Underwater Excavation – The Diving Equivalent Of ‘The Dig’
Produced By: Mike Haigh (Project Director Wreck Hunters)

We owe the dead nothing but the truth’ – Voltaire.

For many, the culmination of work on any archaeological site is the excavation stage. The objective this phase is to discover, record and explain the stratigraphy of the site in order to understand it. In the words of the father of British Archaeology, Sir Mortimer Wheeler, ‘We are not digging up things, we are digging up people.’ This is an unrepeatable experiment. We do not
normally get a second chance.

We should take a moment to consider how we got to this point. The site, in our case a wreck, will have been located; a pre-disturbance survey carried out, a permit granted, and arrangements made for the conservation and display of material from the site. Only then can we move onto excavation.

It is in the excavation phase that the diving archaeologist enjoys an advantage over his/her land-based colleague. Unless blessed with superpowers, the terrestrial archaeologist will not be able personally to ‘fly’ over the site effortlessly as their diving counterparty can. In addition, wreck sites tend not to lie below a great depth of material, such as (in the UK) debris from the Second World War.

From the site survey a master plan will have been developed, which will form the basis of the Diver using a water dredge to excavate a carefully gridded wreck site excavation. It is not easy to discern successive layers of deposit underwater, but it can be done. In the case of the Mary Rose, the remains and deposits from the ship could be distinguished from the ‘gear’ of 19th Century salvage divers, and the occasional losses of objects from pleasure craft travelling over the site. People like to talk about shipwrecks as ‘time capsules.’ Unfortunately, these ‘capsules’ are not sealed.

The trick to making a complete record of the site is careful recording. Every historic object, whether raised or merely observed and recorded in situ must have its own number together with a short label describing what it is. We covered in a previous article the methods for recording and lifting objects. A high level of discipline is needed in all this which hopefully will deal with the
‘diver in the hole’ syndrome – where a diver, having found one object, is lured on by the hope of finding more. Everyone on site must understand that nothing is to be touched, moved or raised until fully recorded. This may be by measurement, drawing, photography or ideally all three. Excavation is destruction, the only justification for which is proper recording. In addition, a whole set of diving safety protocols needs to be in place, as this is, of course, a diving operation.

As with any excavation, below or above water, the logistics need to be carefully planned. There needs to be a working platform, which can range from a simple inflatable to a purpose-built pontoon. Often a substantial grid is erected around the site
for divers to rest on to avoid contact with the remains of the wreck. Most tools used for digging underwater are simple. A lot can be achieved by ‘hand fanning’ and the use of simple tools. But sometimes a compressor needs to be situated on site to run more powerful equipment.

When a lot of material, usually sand or sediment, overlays the site ‘heavy gear’ is often needed to remove it. The three most-used devices for this being the airlift, the water-dredge and the prop wash. The latter was invented by treasure hunters to remove large sand deposits. It works by using the thrust from a vessel’s propeller, directed downward by means of a tube with a right-angle bend. Used carefully, it can be a useful tool; used carelessly, it leaves the site looking like the result of a bombing raid!

For the diver involved in excavation there are two overriding concerns – correct weighting and the cold. You may spend long periods in unusually shallow or deep water where your weighting needs careful attention. Not helped by the fact that you tend to be working in one place without moving much, so not generating much heat. This often results in the need for more insulation and the need for more weight. Most archaeological diving ends up requiring you to maintain close contact with the bottom. Don’t stint on the weight.

This may all seem like an insurmountable tangle of theories and regulations, but it can be done right. Anyone who has done much underwater archaeology will testify to the vividness and excitement which discoveries can give the ‘diving digger’. Don’t miss out on the thrill of discovery and the sense of achievement when a good job is done.

Next time we will be looking at the various methods used to locate ancient wrecks.

Until then I wish you enjoyable and safe diving.