hydrophane noun. 
['hʌɪdrǝfeɪn] L18.[from HYDRO- + Greek -phanēs apparent, phanos bright, clear, from phainein to show.]A white variety of opal that absorbs water and becomes more translucent on immersion.
 ■   hy'drophanous adjective becoming more translucent on immersion 
L18.  [TahlilGaran] English Dictionary ▲