Defining Wreck Diving Restrictions

by Andy Davis

Very few diving agencies go into detail about wreck diving restrictions. Those that do, tend to limit their definition to either ‘not restricted’ or ‘restricted’.

That definition hinges upon whether two divers could pass through simultaneously when sharing gas.  The intention of this is to prevent recreational divers entering areas that they could not easily exit from when sharing gas with a ‘conventional’ short-hose regulator.  

My experiences as a technical wreck and sidemount instructor have taught me that these two definitions are generally too vague to enable clear communication and risk planning on the issue of passing through wreck areas of varied confined space.

Whilst a recreational-trained wreck diver is typically told “no restrictions” and a technical-wreck qualified diver is told “any restrictions”, I have found the later to be less than accurate.

Technical wreck divers are taught to share-air through areas too small to pass side-by-side, but rarely are they taught more refined techniques for safely passing through extremely confined areas.  Such techniques are normally only found on (hard to find) advanced sidemount or top-level, exploration-grade cave courses…

I will attempt to address this deficit, by explaining my own categorization of wreck diving restrictions.

No Restriction

  • Two divers can pass through simultaneously, whilst sharing air (side-by-side or piggyback).
  • No impediment to swift egress from the wreck
sidemount technical wreck diving restrictions

Overhead environment, with no restriction on diver passage, ability to share air or exit simultaneously


  • Two divers cannot pass through easily whilst sharing gas without long-hose.
  • A single diver may pass easily
  • No impediment to swift individual egress from the wreck
sidemount-wreck diving restrictions

Sidemount passage through a restricted area inside a shipwreck. Insufficient space for two divers to pass simultaneously.

Significant Restriction

  • One diver cannot pass through with both cylinders in place
  • Sidemount = detach and push a single cylinder
  • Backmount = remove and push double cylinders/wing
  • Significant impediment to egress from the wreck
sidemount_technical_wreck diving restrictions

Single tank push-through on sidemount – the second tank is still attached.

Major Restriction

  • One diver cannot pass through with either primary cylinders in place
  • Sidemount  = detach and push both primary cylinders
  • Backmount = remove and push doubles cylinders/wing
  • Significant risk of entrapment and delay to egress from the wreck
sidemount overhead environment wreck diving restrictions

Double tank push through on sidemount – to egress a shipwreck through major restriction

Extreme Restriction

  • One diver cannot pass through with both cylinders detached and pushed forwards
  • Impossible to pass through with backmount doubles (even if removed and pushed)
  • Requires leashed trail of one or more cylinders or ‘team pass’ of cylinders through restriction
  • Typically very slow progress through the restriction
  • Possibly a longer restriction, requiring several meters of travel
  • Potentially impossible to perform gas share once within the restriction
extreme wreck diving restrictions

Gas sharing through an extreme wreck diving restriction – both divers pushing and pulling cylinders.

wreck diving restrictions for extreme overhead environment dives

Wriggle through – push short-hose tank, long-hose tank on a hip or ankle leash

About the Author

andy davis technical diving philippines

Andy Davis is a RAID, PADI TecRec, ANDI, BSAC and SSI qualified independent technical diving instructor who specializes in teaching advanced sidemount, trimix and wreck exploration diving courses across South East Asia.  Currently residing in ‘wreck diving heaven’ at Subic Bay, Philippines, he has amassed more than 9000 open circuit and CCR dives over 27 years of diving across the globe.

Andy has published many magazine articles on technical diving, has written course materials for dive training agency syllabus, tests and reviews diving gear for major manufacturers and consults with the Philippines Underwater Archaeology Society.

He is currently writing a series of books to be published on advanced diving topics.  Prior to becoming a professional technical diving educator in 2006, Andy was a commissioned officer in the Royal Air Force and has served in Iraq, Afghanistan, Belize and Cyprus.


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