I don't have "sw", I have "priority=-1" in the options column, and have swap for the mount point. I think it automatically recognized it when it does "mount -a" but I'm not sure. I've reformatted the internal card and would have to retry it.

Normally you can copy the line from /proc/mounts or /proc/swaps into /etc/fstab (and making sure you don't copy noauto).