Super Mario 3 Party: Water Land Under‑the‑Sea Decor & Treasure Hunt Activity

If you walked into our kitchen on party night, you didn’t just see decorations—you entered Water Land. I layered lots of simple, budget DIYs to make it feel like we swam straight into Super Mario 3: moving bubbles, ocean lights, coins, squids and urchins drifting overhead, and a treasure dig for the kids. But before we dive into the decorations, let’s talk about how the kids even got here.

One of my favorite parts of this party was the way each world was introduced. The kids didn’t just wander into the next activity — they earned it. After each challenge, they got to run to a giant Punch Block (DIY tutorial coming soon!) and smash it open. Inside, gold coins rained down along with a letter from Princess Toadstool and a special “tool” they’d need for the next land’s mission.

It gave the whole party the feel of a living video game — they were actually on a quest through different lands to eventually defeat Bowser.

This was the very first letter they received at the start of the party, before heading into any land. It set the stage for their mission:
Retro-style Princess Toadstool letter introducing the kids’ Mario party quest, explaining their mission to travel through four lands and defeat Bowser.
The very first letter from Princess Toadstool, delivered at the start of the party, set the stage for the kids’ mission to journey through four lands and ultimately defeat Bowser.
Once the kids punched their first block, coins fell everywhere and this next letter came out along with their first tool — small toy shovels for the treasure dig.
Mario-themed party letter from Princess Toadstool sending kids into Water Land with tools to complete their first task.
The Immersion Layer (a.k.a. how the kitchen turned into an ocean)

Counters = water: I rolled out long lengths of blue bubble wrap on the counters and island. It looked like rippling water and it was irresistibly poppable for the kids (and, uh, the adults).
Glow + motion: Blue LED string lights rimmed the cabinets, and an ocean‑wave projector/sound machine washed the ceiling with moving “waves” and ambient ocean sounds.
Actual Mario music: I also played the Water Land track from Super Mario 3 in the background so your ears matched your eyes.
Underwater plants: Green streamers twisted into tall “seaweed” and taped to the cabinet doors.
Bubbles everywhere: A small bubble machine rained bubbles during the activity (more on that below).
Wall coins: Yellow paper plates became giant coins on the backsplash.
Super Mario Water Land kitchen decorations with hanging Bloopers and Urchins, seaweed streamers, and blue table covering.
Our kitchen transformed into Water Land, complete with seaweed streamers, coin “tiles,” and hanging Bloopers and Urchins watching over the sandy treasure dig station.
The Ceiling Enemies (DIY Bloopers & Urchins)

Nothing says Water Land like dodging enemies over your head. I made both styles from lightweight bits so they could hang safely and sway a little like they were floating.
Close-up of a purple and yellow Urchin decoration from Super Mario hanging in the kitchen.
One of the spiky Urchin enemies floating above the party — don’t let it touch you!
Close-up of a Blooper enemy decoration from Super Mario hanging in Water Land.
The mischievous Blooper, ready to squirt ink at unsuspecting party-goers.
To make your own underwater enemies, see my Blooper Tutorial and my Urchin Tutorial.
TV screen showing the retro Super Mario Bros. 3 Water Land map, displayed with background music during the themed birthday party.
To complete the immersion, the TV displayed the original Super Mario 3 Water Land map and played the game’s Water Land background music.

The Treasure Dig (the main activity)

This was the kids’ first quest: dig for loot in an indoor “beach.” I set the dig bin on the island so adults could chat nearby while the kids played.
Plastic bin filled with sand, seashells, and gold coins for a Mario-themed treasure dig game.
The treasure dig station — seashells and chocolate coins on top, but the real prizes were buried beneath the sand.
What’s buried down there?

Before covering everything, I loaded the bin with Mario‑themed trinkets (mini figures, stamps, and suction cup balls).
Assorted Mario-themed trinkets and toys laid out in a sand bin before being buried for the treasure dig game.
Before the dig: a peek at all the colorful treasures waiting to be discovered.
DIY “Sand” Recipe

I use this for indoor sensory play because it molds like sand but vacuums easily.
Ratio: ~10 lb whole‑wheat flour : 4 cups canola oil
Mix: Combine in the bin with gloved hands until the texture feels like damp beach sand—crumbly but packable.
Scale: Double or halve as needed; I used enough to fill a large under‑bed storage bin 2–3” deep.
Close-up of oil and flour sand mixture in hand, showing the texture for the treasure dig game.
Our DIY “sand” made from oil and flour — soft, moldable, and mess-free fun.
I set shallow trays around the bin so each kid could sort treasures and keep their finds separate.
Children digging in the sand bin to find Mario-themed treasures at the Water Land station.
Intense concentration as the kids dig for coins and power-ups in Water Land.
Children using tools to dig through sand and uncover treasures in the Water Land bin.
Treasure hunters hard at work, uncovering shells, coins, and Mario-themed surprises.

“Wait…indoors?” (Yes, and it worked!)

Bubble machines and sand usually live outside, but: Florida weather. Since it was just our three kids, indoors made more sense and kept the party flowing.

After the dig: I did a quick pass with a mop to clear the bubble residue and a vacuum to snag stray sand. Cleanup took just a few minutes and the floor was good as new.
Smiling boy wearing a Toad hat standing in front of Water Land decorations.
Big brother Dylan rocking his Toad hat, keeping a watchful eye on the treasure dig.
Wrapping Up Water Land

At the end of the dig, the kids punched their next block, got another shower of coins, and a new letter from Princess Toadstool leading them onward to Sky Land (with cotton balls as their “tool” for the sticky-cloud game). That’s the beauty of structuring the party this way — the kids weren’t just bouncing between random activities, they were moving through a real Mario-style quest.

👉 Next up in the series: Sky Land (with sticky cloud targets) and a full DIY Bob-omb tutorial.

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