The fish does only have the mouth open to eat the Duskmallow Pie bits.
I'll need an Initiative roll from Jub to see if he can use Mage Hand in time before the fish finishes eating the pie if Jub wants to do this. @XxFellsingxX
Since Brut is still convinced that he's a weretiger and therefor immune to mundane damage, could he get advantage on the save? If so, 13. If not, 3.
Brut did take everything from the shop. That would include the needle used to give him the "Lycanthropy".
If he hasn't poked himself with the needle again to take away the "Lycanthropy", he would still be convinced that he's a weretiger. So in that case, he'll have the advantage.
Unfortunately, 13 does not make the save.
The memories of his death in the previous life begin to overwhelm him as he stares into the maw of the giant fish. His body is locking up on him and screaming at him to get away from the creature.
As Brutrumukk collected the items in the shop, he notices that a lot of the items are just junk. The only thing that seems to be of value is the Moonlight Monocle. When Brutrumukk takes the marbles that held their colors, they seep back into his being. The bells on the outfit jingle and ring as he moves about in this jester costume.
He does manage to get the fish's attention, and it does swim to eat the bits of duskmallow pie that was crumbled into the water. Brutrumukk would see the fish open its maw. It's not just large enough to swallow him whole, but it has circular rows of sharp, shark like teeth. The herbs seem to be deep in its gullet now, because he cannot see them in the maw.
But taking in this sight...a primal fear starts to make itself known to Brutrumukk.
Make a Wisdom Saving Throw. This is not a magical effect.
Brutrumukk sees the herbs weren't thrown very far. But he does see that not only has the herbs sunk to the depths, but he also sees a really large fish swallow the herbs whole.