The stormy waters and heavy winds were a great challenge, and almost deemed it impossible for me to succeed, but against all odds I managed to defeat my fears.

against 在这里表示"对抗、反对"的意思。 all 的意思是"全部的、所有的"。 odds 原指"几率、可能性"，引申为"不利条件、困难"。 against all odds 是一个固定短语，字面意思是"对抗所有不利因素"，实际表示"尽管困难重重、在极其不利的条件下"的意思。