GO:0052629:   phosphatidylinositol-3,5-bisphosphate 3-phosphatase activity
Catalysis of the reaction: 1-phosphatidyl-1D-myo-inositol 3,5-bisphosphate + H2O = a 1-phosphatidyl-1D-myo-inositol 5-phosphate + phosphate + 2 H+.