$A=$ area of hole
$\mathrm{V}=$ velocity of water through hole Friction force $=\mu \mathrm{Mg}$ for the vessel to just move
$\rho \mathrm{AV}^{2}=\mu \mathrm{Mg}$
$\rho \times \frac{\pi \mathrm{D}^{2}}{4} \times 2 \mathrm{g} \mathrm{H}=\mu \mathrm{Mg}$
$\Rightarrow \mathrm{D}=\sqrt{\frac{2 \mu \mathrm{M}}{\pi \mathrm{pH}}}$