World Sailing Case 21 states that ‘extraordinary’ and ‘abnormal’ manoeuvres are
unseamanlike.
However, actions that are not seamanlike in a fleet of many boats may be considered
seamanlike in a situation with only two boats. Thus, in match racing some
manoeuvres might be considered normal that would be considered abnormal in other
racing, and therefore ‘seamanlike way’ will be interpreted somewhat more broadly
in match racing.

4. Definition: Room, and meaning of 'in a seamanlike way'
World Sailing Case 21 states that ‘extraordinary’ and ‘abnormal’ manoeuvres are
unseamanlike. Some actions that are abnormal and therefore unseamanlike in a fleet of
many boats will be considered normal and therefore seamanlike in a team race.
However, any manoeuvre that puts a boat or crew at risk of damage is unseamanlike.
The umpires will judge each incident on the basis of the boat’s actions in relation to
the wind and water conditions she is experiencing at the time.

• Racing Rules of Sailing, if the NoR publication day is prior to the publication date of a new version of the RRS
• The Equipment Rules of Sailing, ditto
• Any Class Rules cited in the NoR, which can change much more often than every 4 years
• Any Government Regulations provided by the host country 
• Any Standing Regulations or Rules provided by the host Organizing Authority cited or implied

• RRS would be "World Sailing, Racing Rules of Sailing For 2021-2024, including US Sailing Prescriptions"
• ORC would be "ORC Superyacht Rule 2024" and should Include this link: https://orc.org/organization/rules-regulations
• PHRF on San Francisco Bay would be "Northern California PHRF, Revised January 2022" http://yra.org/wp-content/uploads/2022/01/RulesAndGuidelinesJan_2022.pdf
• One Design Fleet I am a member of "Moore-24 Class Rules Revised 1/23" https://drive.google.com/file/d/1SnN7oFpp_z2FTAi9fXRZoCrCAUKUS2f9/view