A good first aid kit should be stowed on every vessel. The Coast Guard Auxiliary looks for them on their Vessel Safety Check inspection form. First aid kits are a valued safety item, just like a radio or visual distress signal.
Recently Adventure Medical Kits released a first aid kit designed especially for mariners. The company recognized the importance of this equipment and addressed the special needs that boaters require of a medical kit. Components of the medical kits are color coded to match the nature of the injury. A red bag is provided for bleeding or green bag for CPR equipment. The number and variety of component bags is based on the distance you plan to sail away from shore. Greater distances imply less ready access to healthcare professionals.
Adventure Medical Kits for Mariners can range in cost from $850 for an offshore ocean kit to $20 for an inshore kit that could be stowed on a personal watercraft. Each kit, except for the company's smallest version, includes a medical text written by Dr. Eric Weiss and Dr. Michael Jacobs. Titled A Comprehensive Guide to Marine and Travel Medicine, the book is well illustrated and walks you through medical emergencies that might be experienced on a vessel or caused by a water sport.
Dr. Jacobs states that, "We designed the Marine Series for all mariners, regardless of their medical expertise. The supplies, together with our new medical guide in each marine kit, enable the boater to initiate appropriate care for virtually all common minor and major medical encountered at sea and in the marine environment." More on the first aid kits can be seen at Adventure Medical Kits and kits can be ordered from dealers like Fisheries Supply.