Wind main with clones work too. The 3 other targets are random.

What makes op shark bomb outside arena is critical stat. In arena your critic is 0, so shark bomb just gets the basic buff of the skill itself that mean you do not crit that often. So you are eventually guaranteed with 1 chaosed target only. Is way safer for water main to run poison tai and healing setup in zenith mode.

P. S. Water main has another passive, nature energy gathering, that actually is way more op in zenith. A team like normal naruto + kurenai + a healer with her in move 1 with that passive literally lands nukes in round 4+. Who cares about chaos when the enemy gets hit by 5k?