Board Thread:Warhammer 40k General Discussion/@comment-7499389-20130407223055/@comment-6078851-20140601160019

when worn by non-astartes it technically is semi-powered armour, it doesn't become fully-powered armour until connected to an astartes' black carapace.

177.207.31.80 wrote: "In 966.M41, the Tau fought against the Astartes of the Space Wolves Chapter during the War for Kvarium Alpha. On that Ocean World, the Space Wolves' Drop Pods landed deep in the oceans where their occupants, their Power Armour altered by Space Wolf Techmarines to operate in undersea environments, made a move to engage their enemy." power armour is technically an environment suit and as such is air and water tight, but while it can function in space and underwater, that quote clearly shows that they're not suitable, without modification, for the extreme pressures of deep sea environments. i'll bet terminator armour is though :)