Refer to figure.
Firstly, according to:

• ICAO Doc 4444 - 8.8.1 Emergencies [...]

If the pilot of an aircraft encountering a state of emergency has previously been directed by ATC to operate the transponder on a specific code, that code will normally be maintained unless, in special circumstances, the pilot has decided or has been advised otherwise. Where ATC has not requested a code to be set, the pilot will set the transponder to Mode A Code 7700.

• ICAO Annex 17 - 2.1.4 Mode A reply codes:

- Code 7700 to provide recognition of an aircraft in an emergency.
- Code 7500 to provide recognition of an aircraft which is being subjected to unlawful interference.
- Appropriate provisions shall be made in ground decoding equipment to ensure immediate recognition of Mode A codes 7500, 7600 (lost communication) and 7700.

Secondly, maintaining communication with Air Traffic Control (ATC) is important during the whole flight and it is not specifically related to the safety requirements for overwater flights regarding emergency landings.

Thirdly, waypoints in a flight plan is standard procedure for navigation purposes but do not specifically relate to the emergency safety measures for overwater flights too.

Finally, we can determine that life-saving equipment, such as life jackets or lifeboats, be available for all passengers to ensure safety in case of an emergency landing on water should be considered.