Since boyhood Brojen practised swimming in Buriganga River. After his own initiative, the East Pakistan Sports Federation introduced an annual swimming competition in Dhaka in 1953. He was invited to take part in the English Channel Swimming Competition in 1958. As a part of his training he swam in Shitalakshya River, in lower Meghna River and a distance of 46 miles starting from Narayanganj to Chandpur. Prior to the competition, he also swam in the Mediterranean Sea from Capri to Naples.