 Shortly before 02 : 00 on 26 February , while Birkenhead was travelling at a speed of 8 knots ( 15 km / h ) , the leadsman made soundings of 12 fathoms ( 22 m ) . Before he could take another sounding , she struck an uncharted rock at 34 ° 38 ′ 42 ″ S 19 ° 17 ′ 9 ″ E with 2 fathoms ( 3 @.@ 7 m ) of water beneath her bows and 11 fathoms ( 20 m ) at her stern . The rock lies near Danger Point ( today near Gansbaai , Western Cape ) . Barely submerged , it is clearly visible in rough seas , but it is not immediately apparent in calmer conditions . 
