510,000 after two and a half solid days at it. Silent running does work, but in order to be successful, some sharks and subs must be destroyed making it easier to pick up the divers. Set yourself up so that there is only one enemy in each of the four rows. If there is two enemys in each row, get rid of one in each leaving one. if there are three get rid of two in each leaving one. It takes some practice but works for me and as I stated earlier, getting use to the higher speeds of the subs and sharks is a must! Practice, Practice, Practice.