A fiber optic cable (10) having a cable core (20) includes fiber optic cable components in the form of buffer tubes (23), a binder (26), and strength members (31). Cable core (20) includes a series of stripes (38) that comprise a mixture of adhesive and water absorbent substances. The water absorbent substance of stripes (38) is operative to swell and thereby block the flow of water in cable (10). Stripes (38) are made by the sequential coating of the adhesive and the water absorbent substances onto the cable whereby the water absorbent substance is propelled into interstices between the cable components. FIGS. 2 and 4.