Sailing as a sport; a comparison
Here's a comparison to enlarge on the "many skills and subgenres" mention I made in a reply to a forum post asking about sailing:
Tennis: One racquet per player, one ball in play, two to four players, stripes on court to indicate service areas and area for singles or doubles play. Hit the ball over the net and between the lines and try to get an opponent to miss or mis-hit. That's pretty much it; beyond that is some etiquette, score-keeping rules, lots of technique to hit the ball, some sports psychology and tactics for playing the game, and plenty of rehab work for doctors to do once you get tennis elbow. Not to offend tennis fans, but sailing might just be a wee bit more varied:
day sailing, gunk holing, overnight cruising, voyaging, short-duration buoy racing, multi-day regattas, long ocean races, global circumnavigation, world cruising, living aboard
on small single-hander or team-crewed dinghies, windsurfers, kite boards, little catboats and prams, high-performance skiffs or hydrofoil boats, sport boats, small keel boats, cruising boats, racer-cruisers, purpose-built racing boats, small beach catamarans, cruising catamarans and trimarans, volunteering to crew glorious tall ships and museum ships, with crews on elegant yachts and ratty home-built boats all having fun,
sailing in small lakes and ponds, upon inland seas, in bays and gulfs, in the open ocean, in calms and storms, in crowded busy harbors and lonely forbidding coasts, in exotic lands among exotic craft, among ice floes at the top or bottom of the world or anchored among palm trees in a coral-reef-fringed lagoon,
while maybe on the side doing some fishing, surfing, diving and exploring the underwater realms, photography, collecting sea shells or doing nautical crafts, helping with research projects, participating in rendezvous and raft-ups and socializing with other sailors, or using one's skills to help people in less fortunate communities,
learning basic sailing, basic and advanced sail trim, for a boat with one sail or many specialized sails, heavy weather and light air sailing skills and how to be safe afloat under all conditions, anchoring and mooring skills, maintaining and troubleshooting boat systems, learning dead reckoning and piloting, learning celestial and electronic navigation, learning traditional knot and ropework and other skills, perhaps acquiring occupational skills such as sailmaking or boat systems repair or becoming a licensed professional captain or sailing coach or instructor, learning about the ocean and weather, exploring the world and the complexities of all its cultures, learning the tactics and skills of sailboat racing, or perhaps learning about naval architecture and building your own boat or at least customizing and making your boat an expression of yourself and your wants and needs
while sailing your own dinghy as a seven-year-old child, or in high school or college competition, or solo sailing, or sailing in a singles group, or escaping under sail with your family, or being able to include your spouse and children in a sport in which you can compete together with everyone being important to your success, and a sport in which people with disabilities can compete, or sailing for decades after retirement.
Now, THAT's sailing.