IPA: /ˈsiːˌwɜːrθɪnəs/
KK: /ˈsiːˌwɜrθɪnəs/
The quality or condition of a boat or ship that makes it safe and suitable for sailing on the ocean or sea.
Before setting sail, the captain checked the seaworthiness of the vessel to ensure it was safe for the journey.
Seaworthiness is formed from "sea" (from Old English "sǣ", meaning the ocean or large body of saltwater) and "worthiness" (from Old English "wyrðe", meaning having worth or value). The term refers to the condition of a vessel being fit or worthy to navigate the sea safely.
Think of a ship being 'worthy' ('worthiness') to sail on the 'sea' — that's what seaworthiness means.