The Jagalchi fish market is the biggest fish market in South Korea. It is located in the Nampodong/Jagalchi area of the city. To get there take the subway to Nampodong, go out exit 10 and walk towards the sea front. First, there is a large dried sea food market. After having a look at this, walk past the row of vendors and racks of drying fish and you'll reach the indoor market which is filled with lots of weird and wonderful creatures. You can also go through the back doors of the market to get good views over Busan Harbour.
The best bit of the market though as far as I'm concerned is past the indoor market. There is a long line of street vedors selling fish, octopus, shellfish, barbequed fish and just about every sea creature in existence. Behind this area you can stand on the docks and watch the fishing boats being unloaded. This is a busy area and you have to dodge the people, cars and trucks. When we were there an enormous quantity of cuttlefish was being unloaded from the ships and carted off to market. There was so much of it, it was hard to believe there was any left in the sea.
An interesting way to spend a few hours.