Avkrin

Best answer as chosen by Asker / Ratings
1)You have to go to the southern part of the dragon eye lake. There, you'll see a bucket like thing. There, seadramon swims. It's darker and bigger than the other fishes
2)you could use any bait, but it would confuse you because other digimon may like it and there will be lots of heart emotions, so you won't be able to distinguish between seadramon and other fishes. It's best to use a blacktrout, digicatfish or a digiseabas (sorry for the spellings)
3)When the screen gets all yellow and at night. Best to go when the screen is yellow
4)You'll need to get an amazing rod, shogungeekomon gives it (again, sorry for the spelling). It costs 300 merit points which can be earned by trading cards from him. Also, you can ask 3 things from seadramon. First, to be friends, second to learn a technique and third is an item. The item is a digivolution item but be careful, if you are sure it's easy to catch seadramon again than only chose second and third option. Hope I helped!