premise: Brazilian jiu-jitsu is a form of sea fighting.
hypothesis: Brazilian Jiu-Jitsu ( [ dʒuːˈdʒɪtsuː ] [ ˈʒiw ˈʒitsu ] , [ ˈʒu ˈʒitsu ] , [ dʒiˈu dʒiˈtsu ] ) ( BJJ ; jiu-jitsu brasileiro ) is a martial art , combat sport system that focuses on grappling and especially ground fighting .