Subbottom profiling in shallow water: The Akko 4 test case

The paper discusses the detection of shipwrecks embedded in sea-floor sediments using a Chirp sub-bottom profiler. From a methodological-historical perspective it examines four examples of recent chirp recordings of verified shipwrecks embedded in different types of sediment environments, in different geographical and geological areas and from different periods. The effects of shallow water depths, various sediment types, recording speed and different (2D and 3D) sub-bottom profiler systems are briefly discussed. It is concluded that Chirps are well suited for survey purposes, producing high quality 2D profiles of good resolution and satisfactory penetration depth. Furthermore, the equipment is easy to handle from a small boat and allows flexible sailing. This type of 2D data is cheaper and faster to acquire, easier to interpret and apparently also provides better resolution and detail than that from present 3D systems. Chirp data are therefore of great value in identifying and outlining shipwrecks hidden in the sea floor in survey situations where larger areas must be covered. The overall conclusion is that there are grounds for optimism with regard to the application of this method for detection of maritime archaeological targets.