Climbing?.... Swimming?.... I'd say look no further than Shadow of the Colossus. Imagine if the Bismark primal fight was like fighting Phalanx (13th colossus). It doesn't even have to be anything hard or complicated in terms of mechanics. It could just be a buff/debuff where you gain access to a special skill input (similar to the ultros fight when dps goes imp and get the skill "Imp Punch") that allows you to hang on to Bismark when he does a barrel roll.