We have prepared powder samples of ${\mathrm{Na}}_x{\mathrm{CoO}}_2\cdot y{H}_{2}O$ using an alternative synthesis route. Superconductivity was observed in ${\mathrm{Na}}_{0.3}{\mathrm{CoO}}_2\cdot 1.3H_{2}O$ between 4 and 5 K as indicated by the magnetic susceptibility. The bulk compressibilities of ${\mathrm{Na}}_{0.3}{\mathrm{CoO}}_2\cdot 1.3H_{2}O,$ ${\mathrm{Na}}_{0.3}{\mathrm{CoO}}_2\cdot 0.6H_{2}O,$ and ${\mathrm{Na}}_{0.3}{\mathrm{CoO}}_2$ were determined using a diamond anvil cell and synchrotron powder diffraction. Chemical changes occurring under pressure when using different pressure-transmitting media are discussed and further transport measurements are advocated.