News Australia Two marine rescue volunteers have died as they sought to assist a stricken yacht in a deadly rescue mission.  Three people died during the rescue effort as volunteers went to the aid of a yacht at the Ballina Bar in northern New South Wales on Monday night.  NSW Police said four people made it to shore after two vessels got into difficulties in heavy seas. Emergency services were contacted about 6.15pm when a yacht was reported to be in trouble off the South Ballina break wall.  "A crew from Marine Rescue NSW responded, however their vessel rolled while crossing the Ballina Bar in heavy conditions," police said in a statement. "At this time three people are confirmed deceased, while four made it to shore." Police said the search was continuing, with one person believed to be missing from the yacht.  A Marine Rescue NSW spokesman said it had been a terrible night for the organisation.…