During his battle with Charlotte Katakuri, Luffy revealed another form of Gear Fourth known as Snakeman.
Unlike his other two Gear Fourth forms, Luffy does not significantly expand, with his forearms and legs being only slightly enlarged and the rest of his body retaining its normal proportions. The spread of Haki is slightly more limited, as it does not appear to extend onto Luffy’s shoulders and upper body. However, Luffy’s hair becomes flame-shaped like his Haki and sticks up. The steam produced from his body also seems to be draped over his shoulders like a scarf while in this form.
In this form, Luffy gains a significant increase in speed and ability to use “Python” to change the direction of his attacks. Snakeman allows his attacks to continuously accelerate the longer they last, allowing Luffy to not only press an attack more fiercely on an opponent capable of dodging, but increase the attack’s speed and power until he finally lands the hit, and it also gives him the opportunity to attack any area of an opponent with ease.
The techniques Luffy is able to use in this form:
Gomu Gomu no Jet Culverin
A faster version of Boundman’s Gomu Gomu no Culverin. Luffy compresses his fist and releases it, using Python to change the direction of his punch according to the actions of his opponent. His arm speeds up the more it stretches, and the force of the punch was strong enough to smash Charlotte Katakuri into a wall.
Gomu Gomu no Black Mamba
Luffy arches backwards and compresses both arms before unleashing a rapid-fire strike, moving his arms up and down to give the impression of multiple arms moving to attack. As with Jet Culverin, Black Mamba involves Luffy changing the direction of his attacks, but their rapid movements make Black Mamba harder to avoid.
Gomu Gomu no King Cobra
Luffy compresses his arm, and as he releases it, instead of directly targeting his opponent, he has his arm loop around him once before sending his fist flying at his opponent. This gives his attack additional acceleration thus increasing his momentum, before striking his opponent.