Ill be quick cuz i gotta hit the sack: stalk by day and attack by night as much as you can and always have the moon in your back. Carry out first attacks with electric torps as much as possible. Do NOT engage surface ships with your deck gun (should only be used to finish off sinking ships). Dont get too close or your peri will be spotted.
Seach, stalk, destroy, retreat, seach, stalk, destroy, retreat...
G'night!
