This is a guide for River Survival Normal & Hard 1P2C (1 Player, 2 Controller). As Singleplayer relies a lot on CPUs as you can't control both sides you need to collect even more balloons.

Setup

Hold 1 controller in each hand, I prefer the left Joy-Con being P1 and the right one P2 so both of your characters are at the front and you can hold both Joy-Cons in the correct hand.
In minigames, try to keep the left Joy-Con character at the left and the other one at the right, that makes it a lot easier to control both of them. Some minigames randomize the order at the beginning (like "Sort Of Fun"), just switch the controllers if necessary.

Minigames

There are 10 different minigames and you can't get the same minigame twice (unless you collect more than 10 balloons).

• Fireplace Race: 26s plus game time (13-18s) 41-46s
• Miner Setbacks: 23s plus game time (18-23s) 41-46s
• Fetch Quest: 26s plus game time (20-25s) 46-51s
• Penguin Pushers: 25s plus game time (25-35s) 50-60s
• Sort of Fun: 53s
• Net Worth: 54s
• Isthmus Be the Way: 32s plus game time (24-27s) 56-59s
• Home on the 'Rang: 58-59s
• Go With the Flow: 90s
• Suit Yourselves: 119s

Minigames timed by @mdmason85

Route

Always take the very right path for both Normal and Hard: Gentle Beginning > Cheep Cheep Schools > Rapids Run > Eye of the Needle > Beyond the Jungle.

Normal Balloons

5 Balloons is the least you can get, but also hard. You need S rank in all minigames for a 5 balloons run.

• Gentle Beginning: Take the first two balloons (the third one too if you want 6 Balloons).
• Cheep Cheep Schools: Take all three ballons.
• Rapids Run: Don't collect any balloons.
• Eye of the Needle: Don't collect any balloons (In case you have problems with skipping the maze one, collect that one instead of the second one in Gentle Beginnings).
• Beyond the Jungle: Don't collect any unless you need additional time.

Hard Balloons

7 Balloons is the least you can get but one bonk and it's over! You need S rank in all minigames for a 7 balloons run. Reminder that 2 minigames are 90s+ long, so a 9 balloon run adds a guaranteed 1min timeloss!

• Gentle Beginning: Take the first three balloons.
• Cheep Cheep Schools: Skip the first balloon and get all others.
• Rapids Run: Take the second ballon (the others completely kill your speed from the boost panels, on the second one it ends immediately before anyway).
• Eye of the Needle: Only take the notes balloon. In the maze, go the left path and skip the balloon. For a 8 balloons run, take the first balloon too.
• Beyond the Jungle: Don't collect any unless you need additional time.