Within 75 years, parts of coastal Marshfield could be inundated with water daily at high tide, according to a new study of potential sea-level rise in Duxbury, Marshfield, and Scituate. “The results are concerning,” said Paul Halkiotis, Marshfield town planner and project manager for the regional research. Andre Martecchini, an engineer with Kleinfelder in Cambridge, presented the results of the study Monday at Haddad’s Ocean Café in Marshfield to more than 150 people. On parts of Dyke Road and on the Brant Rock esplanade, for example, water could encroach twice a day at high tide, he said in an interview. The company based its report on federal projections of sea-level rise. Additional presentations will be scheduled for Duxbury and Scituate, probably in September, Martecchini said. The information will be incorporated into Marshfield’s upcoming master plan, according to Halkiotis.