They have everything from mackerel, sea squirts (ascidians) and creatures I've never seen before. Most of the people who sell the fish are women, and are called 'Jagalchi Ajumma'.
We made our way to the markets quite early in the morning, so missed all the action of the night time festivities, but we were able to have a great look around.
Jagalchi Station (Busan subway line 1), Exit 10.
Turn right onto Jagalchi 3(sam)-gil Street.
Walk for 5min, then turn left to arrive at Jagalchi Market.
For more information on the Jagalchi Fish Markets, to go the Visit Korea website.