From the Super Mario Wiki
Dream Rafting is a Dream Event that appears exclusively in Mario & Sonic at the London 2012 Olympic Games. It is set in Cheep Cheep River which is based on World 4 from New Super Mario Bros. Wii. The objective is to earn as many points as possible. The starting Olympic Record is held by Team Donkey Kong at 503 points.
When the event starts, players can see three sets of barrels in a right, left, right fashion with indicators to go that direction to collect coins. After the barrels, three Bob-ombs come down from a ledge. Then, there are two short paths with the harder to reach containing three barrel, and the easier containing two. Afterwards, there is a straight path with two Thwomps. Not long after, Cheep Cheeps, barrels, and small waterfalls appear. After the waterfalls, the path splits in two. The left path is a mission to avoid many Thwomps. The other has more barrels containing either coins or Bob-ombs and more Cheep Cheeps. When the paths connect again, a mission to collect ten coins appears. To get coins, the raft needs to hit barrels, but the barrel could contain a Bob-omb. This missions has rocks in the path too. Not long after this mission, is a mission to defeat Porcupuffers with checks to see who ground pounded. After a little bit, there is another mission to collect coins. It is similar to the coin mission before, but a bit longer. Immediately afterwards, the raft goes over a huge waterfall. At the bottom, Gooper Blooper awaits. The mission now is to not fall off the boat. Players who fall in do not come back until the end. However, the players can defeat Gooper Blooper by jumping or Ground Pounding on the four tentacles. At the end, the players are reward based on defeating Gooper Blooper and if anyone fell off. But whether Gooper Blooper is defeated or not, the event then ends, and the players' position is shown.
The Seasoned Sailor challenge is achieved by completing at least 3 missions in one game a number of times in this event. The criteria for unlocking each achievement are as follows:
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