Magikarp/Feebas I guess....
Hey! Nobody answered my question!
This Pokémon resembles an Octorok.
Edit: Sorry, I didn't notice that BrandedOne answered my question. Tentacruel AND Octillery are correct. Tentacruel resembles OoT, MM, WW octoroks, and Gambler's answer, Octillery resembles the original artwork of an Octorok. So both are correct