This will depend on where you want to work. You will be required to have your MEDs and possibly first aid. For example, as a deckhand on BC Ferries, the minimum requirement is MED STCW Basic Safety Training and MED STCW Survival Craft. Canadian Coast Guard will want both of these MED courses with the addition of Marine Basic Fist Aid. You may want to work on a tugboat or fishing vessel and depending on your employer and area of operation, you may need MED A1/A2 (DVS) or MED A3 (SDVS).