Search and Recovery Operations
As a diver you may be called upon from time to time to help to search for valuable objects that have been lost overboard or at sea. These objects, ranging from small personal items to fairly large items of boat equipment, are sometimes dropped into the water and lost. Even when the surface location of the loss is accurately known — or at least is thought to be accurately known — pinpointing its exact location on the seabed is necessary before steps can be taken to recover the item.
For the divers involved, this requires knowledge of underwater search techniques to locate the object, and of techniques appropriate to the size and weight of the object to subsequently recover it.
Course aims:
The aims of this course are to instruct divers in the correct techniques and procedures involved in search and recovery projects, and to provide practical experience of underwater search methods and the use of buoyancy for lifting objects.
Course duration is 2 - days
Theory lessons:
The course starts with a number of theory lessons. In the first lessons, we look at Shotlines, and their different configurations. You will learn how to use such lines to effectively mark the search area. We then move on to the Search operation where we start by looking at the basic search requirements. Before we begin to search for an object, we first need to conduct some research of what the object looks like, the weight of the object, what were the sea condition on the day that the object was lost, the approximate area where the object was lost and finally the type of topography we can expect once on the seabed; all of this information will be needed if an effective search is to be carried out. Once we have this information, we can then look at the many different type search patterns we can use to locate the object; depending on its size and topography. Apart from conducting a manual search, the lesson will cover searches using electronic instruments
Having found the object, we now need to look at the different methods used to recover the object safely to the surface. This will depend on a number of factors; the size, shape and weight of the object, the and delicateness of the object such as, plates and pottery etc. The lesson shows you how to use buoyancy and lift bags in order to lift the object. The lesson will show you how to calculate the in-water weight of the object, the amount of air needed to fill the lift bag and how to control the safe lift of the object.
As part of this theory section there will also be a dry practical session. This lesson is design to introduce you to the equipment that you will use on the dives. We will then survey the object and calculate the dry weight and in water weight. You will be showed the best methods of attaching the lift bag to the object by the use of clips and slings.
Practical lessons:
Over the next two dives, you will get the chance to put all this theory into practice. On the first dive you will conduct a number of different search patterns I order to locate different sizes of objects. The choice of search pattern will also depend on the seabed topography.
Once the object has been located, the second dive will show you how to attach the lift bag to the object. Once this is completed, you will then use compressed air to inflate the lift bag or bags, if multiple bags are to be used, firstly to bring the object to a state of neutral buoyancy and ensuring that the object is equally balanced followed by a controlled buoyant lift of the object to the surface. You will practice a number of different lifting methods, depending on the size, type and fragileness of the object.
