Salander looked up at the board again, staring a bit at the word sea water wondering where are they gonna get that given that they were in the middle of a lake?

Of course the supply pile. So back the Slytherin lad went again with his clay filled planter/tank and measured out the sea water, being very gentle that he doesnt dislodge the newly planted Purple Coral.

He glanced on more time at the board then frowned. Moon calf solution? He looked back, there wasnt anything that said mooncalf solution in the supplies. He made his way back to his desk and saw another piece of paper he failed to notice earlier. Oh lookit that, the instructions for Mooncalf solution.

And that required another trip to the supplies pile.

Cue silent headsmacking.