Golden Retriever is out since you want short fur. Any shedding dog you keep inside will get hair everywhere.
Under 60lbs.... Labs range in size from huge to runt.
Good with kids.... Labs for sure and Golden Retrievers if we hadn't already eliminated it. Of course a even stable pit bull can be good with kids, (I don't recomend that though
) Any dog can be good with kids, but labs are known for being child friendly.
Natural at water retrieving... LAB! and again Golden Retriever if you hadn't minded the longer fur.