which is the best option to join deck cadet. B.Sc. nautical science or diploma in nautical science.

I passed 12th from u.p. board WITH 67.4%. i want to take admission in B.Sc nautical science from IMU what is the process for admission.please tell me the difference b/w B.Sc.nautical science and Diploma in nautical science. is there any exam to join imu, please send me the dates and syllabus.