Fizz ult question

hit

Chum the Waters ACTIVE: Fizz throws a fish in a line that will bind itself onto the first enemy champion it hits, Slow icon slowing them for 1.5 seconds and increasing Fizz's damage against them by 20% for 6 seconds, excluding Chum the Waters's damage. A shark will come out from the earth to eat the fish after 1.5 seconds, regardless of position. SLOW: 50 / 60 / 70% If a champion has the fish attached to them, the shark will Airborne icon knock them up for 1 second. All other enemies within 250-range are Airborne icon knocked away from the shark. All enemies hit are dealt magic damage and are Slow icon slowed for 1.5 seconds afterwards. MAGIC DAMAGE: 200 / 325 / 450 (+ 100% AP) The fish provides sight of its area of effect, and will stay at the location it was thrown to until it binds to an enemy champion or is eaten.

From what I can tell just by analyzing the exact wordage here it would seem as soon as the fish hits/marks that specific champion.