[Steven Lyle Jordan]

Originally Posted by kindlekitten

I didn't get the whole fish thing. let alone the one shark driven sleigh...

Spoiler:

Something about the atmosphere being heavily fluidic, allowing fish to swim/fly through it... the old man's control board created a crystalized boundary (ice) that kept the fish above the city. The shark was the one that had gotten into the bedroom and swallowed half of the Doctor's screwdriver. Retrieving the screwdriver made the shark ill, and when they nursed him back and set him free, they tamed him, and were able to call him back with the screwdriver and hook him up to the sleigh...

(Boy, did that sound stupid!)