It is very important to be aware of emergency communications options and protocols when you are kitesurfing. Bear in mind that kitesurfers are classified as "sailing vessels".
In Australia dial 000 (triple zero) and ask for Police for an emergency
Write your name and phone number on your boards and kites so if you lose one and they are found you can be easily contacted.
If you lose equipment on the water notify emergency services (e.g. Water Police) so that they don't start a search if is found.
Emergency telephone calls
Find out the local number for reporting and emergency situation. This varies across different regions and countries.
In Australia dial 000 (triple zero) and ask for Police for emergency related matters.
The operator will route the call to the appropriate Police resource.
There is a common misconception that you only dial this number when there is "grave and imminent danger" - when actually the Police would prefer to get an important/relevant call early so they can take appropriate action early.
You should call 000 again to report an issue has been resolved if you are not in direct contact with emergency services responders.
If in doubt, call it in. Emergency response by boats and air time for helicopters is very expensive and best avoided.
Marine VHF radio
You can use a marine VHF radio (instead of 000 call) to notify the Coastguard and/or Water Police of incidents, requests for assistance etc.
You can keep a portable unit in your car and carry it on a downwinders (if is waterproof).
Use Channel 16 for initial "distress" call. The Coastguard may then ask you to move to another channel for further comms. - e.g. 72 (Recreational Vessels) The Coastguard will escalate to Water Police or other emergency services if required.
See VHF radio channels for a full list of marine VHF channels.
International radio protocol options to use at the start of your message are:
"Mayday, mayday, mayday" - emergency assistance required immediately, grave and imminent danger, possible loss of life etc.
"Sécurité, sécurité, sécurite" - navigational warnings, important messages etc.
"Pan-pan, pan-pan, pan-pan" - signify there is an urgency on board a boat, ship, aircraft etc. but that there is no immediate danger to anyone's life or to the vessel itself.
Information to provide
Information to relay after and emergency call and/or alert should include:
identification of the kiter/gear
nature of the problem
type of assistance or advice required, if any
your contact details (name, call sign, mobile number etc.)