▁manage ▁this ▁risk . ▁Limited ▁visibility ▁div ing ▁can ▁cause ▁dis orientation , ▁potentially ▁leading ▁to ▁loss ▁of ▁sense ▁of ▁direction , ▁loss ▁of ▁effective ▁bu oy ancy ▁control , ▁etc . ▁D ivers ▁in ▁extremely ▁limited ▁visibility ▁situations ▁depend ▁on ▁their ▁instruments ▁such ▁as ▁d ive ▁lights , ▁pressure ▁gau ges , ▁comp ass , ▁depth ▁gauge , ▁bottom ▁timer , ▁d ive ▁computer , ▁etc ., ▁and ▁gu idel ines ▁for ▁orientation ▁and ▁information . ▁Training ▁for ▁cave ▁and ▁w reck ▁div ing ▁includes ▁techniques ▁for ▁man aging ▁extreme ▁low ▁visibility , ▁as ▁finding ▁the ▁way ▁out ▁of ▁an ▁overhead ▁environment ▁before ▁running ▁out ▁of ▁gas ▁is ▁a ▁safety - crit ical ▁skill . ▁ ▁Equ ip ment ▁ ▁Techn ical ▁divers ▁may ▁use ▁div ing ▁equipment ▁other ▁than ▁the ▁usual ▁single ▁cyl inder ▁open ▁circuit ▁sc uba ▁equipment ▁used ▁by ▁recre ational ▁divers . ▁Typ ically , ▁technical ▁div es ▁take ▁longer ▁than ▁average ▁recre ational ▁sc uba ▁div es . ▁Because ▁a ▁decom pression ▁oblig ation ▁prevents ▁a ▁diver ▁in ▁difficulty ▁from ▁sur f acing ▁immediately , ▁there ▁is ▁a ▁need ▁for ▁redund ancy ▁of ▁breath ing ▁equipment . ▁Techn ical ▁divers ▁usually ▁carry ▁at ▁least ▁two ▁independent ▁breath ing ▁gas ▁sources , ▁each ▁with ▁its ▁own ▁gas ▁delivery ▁system . ▁In ▁the ▁event ▁of ▁a ▁failure ▁of ▁one ▁set , ▁the ▁second ▁set ▁is ▁available ▁as ▁a ▁back - up ▁system . ▁The ▁backup ▁system ▁should ▁allow ▁the ▁diver ▁to ▁safely ▁return ▁to ▁the ▁surface ▁from ▁any ▁point