It sure is a chick. Although vent checking is harder on chicks then geese, that's about the only way to clearly tell at that age and i can't pick it up.
It’s pretty early to tell the sex. If you posted pictures again in 3-5 weeks then it would be a lot easier to tell. I think you are right about it being a splash Cochin. I’m not very familiar with Cochins though.
If it has a single comb and the bottom of its feet are yellow then you have a Cochin. Much to young to sex just now. I'd say its a blue not a splash. A splash should be a little lighter and have a lot more black feathers.