well. I have a Portie (Portuguese Water Dog) that nearly fits the bill, but is too large (40lbs) but he thinks he's small and sleeps on top of me every night. I'd recommend this breed, but they are larger than you are looking for.
PT Water Dog?! Excellent choice, kind with childrens and loyal to his master, loves to swim...being a local breed, since my childhood i've had several and always my choice.