I voted Mudkip
Mudkip is my favorite water starter, but it was difficult to choose because I also love Oshawott. But because Mudkip was my first, I gave it the vote, but Oshawott comes in a very close second.
1. Piplup (IT'S SO CUTE! dont know why, but i was just drawn to it the moment i saw it)
2. Totodile (first pokemon i ever had, and ive always loved it and all of its evolutions)
3. Squirtle (turtles are my favorite animal, and it was my favorite pokemon as a kid)
4. Mudkip (i still like it, just not as much as the others)
5. Oshawott (only hated it in BW because of its horrible artwork)
Totodile is my favorite Water starter. It has an adorable design, Feraligatr was really good in my HG team and since it was the first Water starter I used, I have a bit of a soft spot for it. Oshawott would be in second due to having a really cute design in both its first and second form and Samurott is pretty cool. While I think that Swampert is the most useful out of the final Water starter forms, Mudkip would be in third since I prefer the designs of its evolve forms over its basic form.
Piplup, because It's very cute, plus it's powerful too. Plus when it evolves into Prinplup, it gets really cool, and even more powerful, and when it evolves into Empoleon? Times Prinplup by 10x, and then some.
Oshawott is a close secound, because it's cute and cool, and it's evolutions are cool and powerful. Plus I really like it in the anime. To bad though that GF or Nintendo really messed up their offical artwork.
Totodile is third because of those aligator fangs. Gotta love those fangs.
Squirtle is fourth pretty much because I like most the other Water-Type starters more. Not that I don't like Squirtle or anything. I just like Piplup, Oshawott, and Totodile even more.
Mudkip gets pretty much the same treatment as Squirtle.
So, do I prefer turtles, crocodiles, mud skippers, penguins, or samurai otters and sea lions? Well, I can't take a pass on Oshawott, as I think it (and its evolutions) is cooler than all the other Water-type starters. Besides, it is my favorite starter, after all.