Lava

Lava is an element found exclusively in the fanon series of Pikmin. There are two types of lava. Shallow lava burns Pikmin when they touch it, but Red Pikmin can pass unharmed. Deep lava is similar to acid because it takes the form of a liquid, and that it causes Pikmin to die instantly. However, even Red Pikmin die when they touch deep lava.

Some enemies also utilize shallow lava as a weapon, for instance, the Clown Around squirts jets of lava from the flower on its chest. Some enemies also use lava as a defense mechanism, like the Lava Goolix, which is composed of the molten goo. Red Pikmin generally should be used against lava-wielding enemies.

Pikmin: Connection of the Worlds
There is regular lava in this game, then there is a hotter variant, known as magma. Lava appears a reddish color, with cool, dark spots scattered around. Red Pikmin are resistant to lava. Underground, the lava is called magma as it has not reached the surface yet and is hotter. This is because the magma is closer to the mantle. It is more runny than lava, hotter than lava, and looks an orangish-yellowish color. Burgundy Pikmin are resistant to magma, but are also resistant to lava. Any other Pikmin that touches lava or magma will be incinerated. If a captain touches lava, they will lose 30% of their health, and if they touch magma, they will lose 70% of their health.

Pikmin: Forces of Evil
In Pikmin: Forces of Evil, lava is a fairly-rare hazard first found in Zebes that does steady damage to Olimar when submerged and fries all Pikmin that aren't Red Pikmin. After fighting the Ridley boss, Olimar gains access to the Heat Shield Upgrade that reduces the drain on Olimar's suit integrity by 60% (but unlike the Metroid series' Varia Suit, it doesn't reduce enemy damage.)

Pikmin: Theme Park
Lava is a hazard exclusive to Heatwave Rollercoaster and its caves, and only has a deep variant. Crimson Pikmin, as well as being able to resist fire, can swim in this.