In this case the biconvex lens will behave as a diverging lens because the refractive index of water (1.33) is more than that of the lens(1.25).
1f=(μr−1){1R1−1R2}
1f=(μlμs−1){1R1−1R2}
ifμl<μs,thentheresultofaboveformulawillbedominatedbynegative,
whichmeansfocusshiftsaboutthepoleofthelens,
whichmeansthenatureofthelenswill
bechangedfromconvergingtodiverging