Search and Recovery Search 1 SR v1.2 Copyright © BSAC 2009 Search Operations

Search and Recovery Search 2 SR v1.2 Copyright © BSAC 2009 Outline Hazards of search and recovery dives Requirements for an effective search Research stages Types of searches: ●small area ●large area Surface searches and technology General advice

Search and Recovery Search 3 SR v1.2 Copyright © BSAC 2009 Hazards Entanglement Low visibility – stirred up silt ●buoyancy control Currents Task fixation ●monitor yourself and your buddy Minimise hazards by using safe diving practices

Search and Recovery Search 4 SR v1.2 Copyright © BSAC 2009 Search requirements Simple Cost effective – in dive time Know which areas have been searched Navigation Adaptable ●differing natures of sea bed ●weather Planned simple cost effective 100% coverage navigable adaptable planned

Search and Recovery Search 5 SR v1.2 Copyright © BSAC 2009 Research stage Important to research and plan well ●divers must know what to look for ●size of lost object (battleship or bracelet?) ●how buoyant is the object ●where was it lost ○were marks taken? ○how accurate are the marks? ●time/tide/weather conditions when object was lost Estimated likely position now – limit search area

Search and Recovery Search 6 SR v1.2 Copyright © BSAC 2009 Types of search Choice depends on: ●size ○of lost object ○of search area ●seabed ●depth ●equipment/resources available ●visibility ○small object/small area ○large object/large area ●water movement ?

Search and Recovery Search 7 SR v1.2 Copyright © BSAC 2009 Grid search Good for finding small items Effective for very small areas 100% coverage possible Need lots of time Labour intensive Often used for archaeological surveys

Search and Recovery Search 8 SR v1.2 Copyright © BSAC 2009 Jackstay search Shotweight Jackstay line

Search and Recovery Search 9 SR v1.2 Copyright © BSAC 2009 Moveable jackstay search Effective for large areas Distance line is moved depends on visibility Little equipment required 100% coverage can be ensured

Search and Recovery Search 10 SR v1.2 Copyright © BSAC 2009 Jackstay and parallel baselines

Search and Recovery Search 11 SR v1.2 Copyright © BSAC 2009 Circular search

Search and Recovery Search 12 SR v1.2 Copyright © BSAC 2009 Circular search uses Effective for small areas Little equipment required Distance between circles depends upon visibility 100% coverage can be ensured Use pendulum/sweep search if full circle not possible

Search and Recovery Search 13 SR v1.2 Copyright © BSAC 2009 Compass searches Require very little equipment Hard to control Can’t guarantee 100% coverage Where possible use cardinal points Control leg lengths by timing/counting fin-strokes Leg lengths determined by visibility Navigate/look

Search and Recovery Search 14 SR v1.2 Copyright © BSAC 2009 Compass search patterns Start Square spiralZig-zag

Search and Recovery Search 15 SR v1.2 Copyright © BSAC 2009 Swimline search

Search and Recovery Search 16 SR v1.2 Copyright © BSAC 2009 Swimline search Quick coverage of large area Uses many divers One diver follows baseline Hard to control Distance between divers depends on visibility Can use weighted line to snag objects

Search and Recovery Search 17 SR v1.2 Copyright © BSAC 2009 Surface search Quick coverage of large area Only useful for large objects Requires position fixing ●visual ●GPS Needs target detector ●electronics ●physical

Search and Recovery Search 18 SR v1.2 Copyright © BSAC 2009 Echo sounders Principles of sonar ●transducer emits sound pulses ●time delay of reflected pulse indicates on depth ●results displayed on scrolling screen ●strength of echoes often colour coded Using echo sounders ●beam angle affects footprint and definition ●screens need interpreting ●read the manual ●practise, practise, practise! Boat Screen

Search and Recovery Search 19 SR v1.2 Copyright © BSAC 2009 Other target detectors Olex Magnetometer Sonar ●side scan ●multibeam

Search and Recovery Search 20 SR v1.2 Copyright © BSAC 2009 Surface search tactics Search patterns Search datum ●electronic marker ●shot Consider ●sonar footprint v lane width ●wind/tide/sea state ●shape of target Spiral search Square spiral search Rectangular search Tide NO YES

Search and Recovery Search 21 SR v1.2 Copyright © BSAC 2009 Making life easier Preparation ●use prepared ropes and clips ●use adequate shot weights and buoys ●practise on dry land and/or in shallow water Execution ●use shot-line for transport ●in tidal flow work into the current ●overlap search lanes ●on uneven seabed remember to look behind rocks ●mark object once found!

Search and Recovery Search 22 SR v1.2 Copyright © BSAC 2009 Summary Do your research well Use appropriate search technique for the lost item Keep it simple Use pre-prepared kit Aim to ensure that 100% of area is covered Know which areas have been searched

Search and Recovery Search 23 SR v1.2 Copyright © BSAC 2009