Relative rate of hydrolysis of the carbon chlorine bond in thioethers and ethers
This is a classic case of neighboring group participation. The hydrolysis of the thioether is significantly faster because the sulfur can displace the chlorine to give a three member ring with a sulfur in it. The ring is quite reactive and will easily be opened by water.



For reference, you can also look at a compound like mustard gas. It has the same functional groups and is so reactive that is a war gas.