  The root mean square radii of the proton density distribution in $^{16-24}$O
derived from measurements of charge changing cross sections with a carbon
target at $\sim$900$A$ MeV together with the matter radii portray thick neutron
skin for $^{22 - 24}$O despite $^{22,24}$O being doubly magic. Imprints of the
shell closures at $N$ = 14 and 16 are reflected in local minima of their proton
radii that provide evidence for the tensor interaction causing them. The radii
agree with it ab initio calculations employing the chiral NNLO$_{\mathrm{sat}}$
interaction, though skin thickness predictions are challenged. Shell model
predictions agree well with the data.
