Sega Marine Fishing is a fishing simulation game in which the player attempts to catch various marine sport fish. The gameplay's emphasis was on enticing fish to bite onto the lure and then successfully fighting the fish and reeling it to the boat. As the player catches fish, they earn item cards. Items earned with these cards include fish and artifacts for an aquarium, fishing equipment, additional boats, and various goofy accessories such as different colored shorts. The game also featured two modes of online play: tournament fishing and "fish mail". In tournament fishing, players competed to catch the biggest fish within a species. Fish mail consisted of writing short messages. Players could receive random messages by catching fish.