Unsure about yachting, but one thing you'll need is to be a member of Rega.ch, which costs 30 SFr/year.  Should they ever have to come to save you with their helicopter, the expenses involved will be covered - phew! ...It's also covers similar transport for car-accidents and various mountain related problems.  

Stay safe!  :o)  JT.

For normal accidents (hiking and I guess sailing as I don't see sailing (at least in Switzerland) to be too risky) there is the accident insurance.

There are two types: If you are employed, you ought to be insured by your employer, usually SUVA http://www.suva.ch/english/startseite-en-suva.htm.

If not, you have the option to include it in your normal, basic health insurance.

http://www.bag.admin.ch/themen/versicherung/00321/00335/index.html?lang=en

Found this:

Non-occupational insurance is automatically part of the insurance package, provided that the insured person works at least eight hours a week for the same employer in a company that is covered by Suva's insurance remit. As with occupational accident insurance, non-occupational insurance covers the medical and financial expenses that arise after a non-occupational accident. Employers generally deduct the premiums for non-occupational accidents from employees' wages and pass them on to Suva directly.

http://www.suva.ch/english/startseite-en-suva/versicherung-en-suva/nichtberufsunfall-en-suva.htm