▁reducing ▁the ▁risk ▁of ▁being ▁unable ▁to ▁find ▁the ▁way ▁out . ▁A ▁lif eline ▁fixed ▁to ▁the ▁diver ▁is ▁more ▁reliable ▁as ▁it ▁is ▁not ▁easy ▁to ▁lose , ▁and ▁is ▁often ▁used ▁when ▁div ing ▁under ▁ice , ▁where ▁the ▁line ▁is ▁unlikely ▁to ▁sn ag ▁and ▁the ▁distance ▁is ▁reason ably ▁short , ▁and ▁can ▁be ▁t ended ▁by ▁a ▁person ▁at ▁the ▁surface . ▁St atic ▁gu idel ines ▁are ▁more ▁suitable ▁when ▁a ▁lif eline ▁is ▁likely ▁to ▁sn ag ▁on ▁the ▁environment ▁or ▁on ▁other ▁divers ▁in ▁the ▁group , ▁and ▁may ▁be ▁left ▁in ▁situ ▁to ▁be ▁used ▁for ▁other ▁div es , ▁or ▁recovered ▁on ▁the ▁way ▁out ▁by ▁w inding ▁back ▁onto ▁the ▁re el . ▁Guide ▁lines ▁may ▁be ▁very ▁much ▁longer ▁than ▁lif elines , ▁and ▁may ▁be ▁branch ed ▁and ▁marked . ▁They ▁are ▁used ▁as ▁standard ▁practice ▁for ▁cave ▁div ing ▁and ▁w reck ▁pen etr ation . ▁ ▁Ext rem ely ▁limited ▁visibility ▁Techn ical ▁div es ▁in ▁waters ▁where ▁the ▁diver ' s ▁vision ▁is ▁sever ely ▁imp eded ▁by ▁low - visibility ▁conditions , ▁caused ▁by ▁tur bid ity ▁or ▁s ilt ▁out ▁and ▁low ▁light ▁conditions ▁due ▁to ▁depth ▁or ▁en closure , ▁require ▁greater ▁compet ence . ▁The ▁combination ▁of ▁low ▁visibility ▁and ▁strong ▁current ▁can ▁make ▁div es ▁in ▁these ▁conditions ▁extremely ▁ha z ard ous , ▁particularly ▁in ▁an ▁overhead ▁environment , ▁and ▁greater ▁skill ▁and ▁reliable ▁and ▁familiar ▁equipment ▁are ▁needed ▁to