Help with description of "Chum the Waters"

I have a question about this move. The way it is described here makes it sound like the damage amplification buff would apply on the fish hit; however, I have many friends telling me it is not that way, and instead the damage amplification buff comes after the shark (when the icon pops up above their heads). I was just wondering which one it is, because this move description even says "except chum the waters" which makes it even more confusing and would make me think that in order to exclude the bonus damage it would be on the fish tag. Also the second sentence of the description looks to be talking about the second part of the move because that all has to do with when the shark erupts. Anyways any clarification is much appreciated.

Chum the Waters Cost: 100 Mana Range: 1275

Fizz releases a magical fish toward a location attaching to any champion that walks over it, slowing their movement by 50/60/70% and amplifying magic damage by Fizz (except Chum the Waters) to the target by 20% for 6 seconds. After 1.5 seconds, a shark erupts from the ground, knocking up the target and knocking other enemies aside dealing 200/325/450 (+100% Ability Power) magic damage and reducing their Movement Speed by 50/60/70% for 1.5 seconds.