Roronoa Zoro's bloodline
-This thread contains spoilers-
-Theory made by a friend some time ago-
Roronoa Zoro’s bloodline
Zoro's heritage remains largely unknown. Shimotsuki is not so much his birthplace as it is the village he settled in to learn at the dojo there when he was younger. His actual family remains unknown, though it's difficult to tell whether Zoro knows them or not. Wherever he came from before staying in Shimotsuki, he's never seen returning to it or to anyone who might've been there. That’s right; this is a theory about his bloodline.
This might be shocking for you, or just plain stupid, but I believe that Zoro is part fishman. Well, at least let me explain before you leave the thread or start commenting.
The first thing I’m going to mention is his green hair, something that has been standing out since the first chapters of One Piece. In a world where blue, pink, and even purple are seemingly normal and acceptable hair colors, Zoro's green hair still manages to come off as strange. Sanji's habit of calling him 'marimo' is a jab at this.
Yes, if you think about it carefully, you’ll notice that there aren’t a lot of characters with this hair color, green that is. So which characters do have green hair?
Well, there was one of the orangutans from the Jaya Arc. There was also Fukuro from Enies Lobby (the impossibly round member of CP9 with a zipper for a mouth). There's Boa Hancock's sister, Sandersonia, who's tall even for an Amazon with a very wide head disproportionate to her body. In addition to having green hair, all three of these characters have much stranger appearances, if not being an entirely different species altogether.
Of those that look more normal for having green hair, there are three very notable examples. The first is Keimi, who we know to be a mermaid herself. The second and third characters are a supporting duo from the Water 7/Enies Lobby arcs: Kokoro and her granddaughter, Chimney.
And just a little note, Kokoro and Chimney do really have slightly green hair in the manga, though their hair in the anime was shown as blonde.
With that in mind, it's interesting to note that aside from Zoro, three of these green-haired individuals are related to a mermaid while the other three are either another species or have a very strange appearance in addition to their hair color.
Another thing about green hair characters, Makino from Luffy’s hometown has been seen with green hair in the anime, though she has black hair with slightly dark green stripes.
As was pointed out in a recent chapter of One Piece, Fishman and Mermaids are known to breed with one another, with variable results in their offspring. Pappug is seen explaining this when Luffy noticed a Fishman father with both a Fishman and Merman. From the way it's explained, such a family isn't even that unusual there.
Throughout the series, we’ve actually seen half man-half fishman characters, and one of them Sapi. You may know him better as 'that guy Sanji got the elephant tuna' from Logue town, and his heritage was revealed in the second databook.
Interestingly enough, despite his mostly human appearance, Sapi is actually stated to be half-fishman. To go back to what Pappug explained to Luffy, this could simply be because he took more after his human heritage than his fishman, much the same way that a baby merman could bear no immediate resemblance to his fishman father.
Since Sapi has never made an appearance again, there's not much we can say about whether or not he has abilities similar to that of a fishman. However, we've seen a little more with our other two examples.
Big Pan, a giant who was part fishman, has both the strength of a giant and fishman, for instance. He's not as tall as a pure giant (though the anime made him as such), only about two or three times the size of a regular human (making him shorter than people such as Bartholomew Kuma or Gecko Moria). Big Pan also had slippery skin like a mudfish, which came in handy for him during the Groggy Match with Sanji and Zoro, though he lacked gills or webbed fingers.
As for Chimney, while she might not look remotely like a mermaid she's proven to be a very strong swimmer, going so far as being able to rescue Luffy from drowning in the Enies Lobby arc. That's a pretty big feat for such a small girl, given that Luffy is twice her size and would've been a hammer in the water. Oda has said himself that the only reason she was able to do so was because of her mermaid blood. So it would seem that even if appearances weren't passed down, the skills of a mermaid were, diluted though they may be.
So how does all of this pertain to Zoro? While the green hair speaks for itself (if it is indeed an indicator of fishman/merfolk genetics), let' sapply the points made on the abilities of fishman and/or mermaid hybrids to him here. After all, Zoro himself has shown some interesting abilities over the course of the series.
It needs not be said that Roronoa Zoro possesses skills far greater than your average human. As far as strength goes, I like to think that's all homegrown on his part, but I can't lie. Him turning out to have fishman blood would make some of those feats of strength a little more plausible by the rules the One Piece world follows.
But additionally, that strength is likely the least noteworthy in support of this argument. Zoro has actually proven himself to be a decent swimmer himself. There's a reason why it's usually him or Sanji seen rescuing someone who goes into the water. That said, there are at least three instances than I can think of in which Zoro proved to be a regular fish to water. ...do pardon the pun.
The first of these was on Skypeia, when he, Nami, Robin, and Chopper were looking for a way off the altar. As it was surrounded by sky sea, they were thinking maybe they could swim. As it would turn out, the area was infested with sky sharks, and Zoro ended up fighting one on its own turf.
One thing that should be noted about sky seas: while you can swim through them like regular water (and they do indeed have the same effects on a Devil Fruit user), they're notably lighter than a regular sea. While this would've worked to Zoro's advantage, the same could be said for the sky shark. At one point, he was dragged down out of view from the others long enough that Nami and Chopper were worried that he'd been eaten. Zoro surfaced moments later, punching the creature out as he did so.
The next instance was towards the end of Water 7, after Luffy and Zoro confronted Rob Lucci. Defeated quickly, Lucci tossed both of them out of the building. Thanks to Aqua Laguna (an annual high tide that engulfs the lower half of Water 7 in water), part of the city was taking water already, which is where Zoro landed. Despite how far he flew and the storm picking up, he managed to swim to safty. Well. Until he got stuck in a chimney, but that's another story. The point is: he didn't drown.
Last but not least, the most recent example on Fishman Island. As Ryuugu Palace was flooding during the attack of fishman Hodi Jones and his men, Zoro ducked underwater to fight him. As a reference back to the first time the crew had to fight fishmen, this was an incredibly dangerous thing to do as fishmen are twice as fast and powerful underwater than they are on land - and they are typically superior there as well. However, Zoro managed to act both stronger and faster under water, nothing to be surprised about though.
So my theory is basically that Zoro is part fishman. There’s a possibility that one of his parents was a fishman/mermaid, though he got his looks from the one who was human. This is really just wild guessing though, so no need to start a heavy discussion about it. Just tell me what you think about it, thanks for the attention.