I would save the child first and it is not because of what other people think and what is the general tendency of the society. I would save the child first keeping in mind that a child does not have that much skill and experience as compared to an adult to deal with such life threatening situation and that will be the sufficient reason for me to save child first and the spouse next. Spouse being an adult is no doubt more capable than a child to save herself to some extent.
It is not like that whom you love the most, rather it is more to do with who needs the help most and that sets the priority under such circumstances. In that sense, a child is always the top most priority.