Sponge

The Sponge is a set of tires in the Mario Kart series.

Mario Kart 7
The Sponge tires first appear in Mario Kart 7, where they are an unlockable kart part. They offer an acceleration boost that is tied with the Wood tires, but they also hinder speed and weight. In fact, the Sponge tires offer the second lowest weight boost, the lowest being the Roller tires.

In terms of their hidden stats, the Sponge tires excel very poorly while underwater, but their air stats are given a strong boost to make up for it.

Mario Kart 8 / Mario Kart 8 Deluxe
The Sponge tires also appear as an unlockable kart part in Mario Kart 8, where their appearance has been altered to an extent. Their stats have also been modified a bit in that they do not boost acceleration as much, and they are not as light as before. Their handling does get hindered to boost traction, however.

Much like in Mario Kart 7, the Sponge tires are among the worst when it comes to underwater performance, but they do get a mini-turbo boost to make up for it. The Sponge tires share their stats with the Wood and Cushion tires.

In Mario Kart 8 Deluxe, the Sponge tires are available from the start. Their water speed is slightly better, they do not boost acceleration anymore, and their traction has been slightly reduced as well. The Sponge tires now only share their stats with the Cushion tires.

Statistics
Stat values are out of 6.

Mario Kart 7 stat boosts

 * Speed: -0.25
 * Sea Speed: -1
 * Air Speed: +1
 * Acceleration: +0.5
 * Weight: -0.75
 * Handling: 0
 * Sea Handling: -1.25
 * Air Handling: +1
 * Off-Road: 0
 * Mini-Turbo: 0
 * Stability: 0
 * Drift: +1

Mario Kart 8 stat boosts

 * Ground Speed: -0.25
 * Water Speed: -1
 * Air Speed: +0.25
 * Anti-Gravity Speed: -0.25
 * Acceleration: +0.25
 * Weight: -0.25
 * Ground Handling: -0.25
 * Water Handling: -0.5
 * Air Handling: 0
 * Anti-Gravity Handling: -0.25
 * Traction: +0.5
 * Mini-Turbo: +0.25

Mario Kart 8 Deluxe stat boosts

 * Ground Speed: -0.25
 * Water Speed: -0.5
 * Air Speed: +0.25
 * Anti-Gravity Speed: -0.25
 * Acceleration: 0
 * Weight: -0.25
 * Ground Handling: -0.25
 * Water Handling: -0.5
 * Air Handling: 0
 * Anti-Gravity Handling: -0.25
 * Traction: +0.25
 * Mini-Turbo: +0.25

Names in other languages
Schwamm