Believe it or not just getting on any ferry/ship and catching that odour of oil, paint and salt. Takes me staright back to my days in the RN.

Above that the smell of wood being cut or sawn. My dad was often away for long periods when I was a lad (navy too), so when he came home, which was infrequent, he would get on with all the jobs around the house, he especially loved doing woodwork and carpentry. So the smell of fresh cut wood was always a reassuring sign he was at home.