Does the focal length of lenses change if it is immersed into water ? Explain in brief.

Yes the focal length of lense changes if it is immersed in water.This can be explained with the help of Lensmakers formula.
According to this formula the focal length of lens depends on refractive index of material of the lenses.
The refractive index changes if the lense is immersed in water which accordingly changes the focal length of lense.