Leaving the shore behind is the fun of boating. Everyone relaxes as they wave goodbye to everyday stresses for a time. Yet boaters are also bidding medical assistance adieu, so it’s important to know all you possibly can about detecting and responding to heart attacks and cardiac arrests.
Risks for heart failure are greater for the elderly and those with diagnosed conditions, but some risks escape attention. Heart issues may also occur after accidents, falls, immersion into cold water, near-drowning inhalation of water, and heat stroke.
According to the American Heart Association, symptoms of a heart attack include uncomfortable pressure, squeezing, fullness, or pain in the center of the chest that lasts more than a few minutes or that goes away and comes back; pain or discomfort in one or both arms, back, neck, jaw, or stomach; shortness of breath (with or without chest discomfort); and/or breaking out in a cold sweat, nausea, or lightheadedness. The most common heart attack symptom for all genders is chest pain or discomfort but women are more likely than men to experience shortness of breath, nausea/vomiting, and back or jaw pain.
A cardiac arrest presents differently than a heart attack. The American Heart Association advises to suspect cardiac arrest if a person isn’t breathing, is only gasping for air, or there’s a sudden loss of responsiveness without speaking, blinking, or other 
reaction even if you tap him or her hard on the shoulders or ask loudly if he or she is OK.
Cardio pulmonary resuscitation (CPR) is administered to a person whose heart has
stopped beating to keep blood flowing to the brain. Most heart attack victims die before they reach the hospital, so keeping someone alive long enough for doctors to discover what is blocking the heart provides a greater chance of survival. CPR must be done in conjunction with immediately summoning rescue personnel. [Note: when in doubt as to what someone aboard is experiencing, summon help and take measures to keep the blood flowing anyway. Better to be wrong than you know what.]
Skippers and crew should take a comprehensive CPR course (one that includes other emergency first aid is best). No matter how near or far from shore you boat, keeping someone alive is crucial until first responders arrive.
Find a CPR course: http://ahainstructornetwork.americanheart.org/AHAECC/classConnector.jsp?pid=ahaecc.classconnector.home
https://www.redcross.org/take-a-class/cpr
Video: Hands-only CPR
