When speaking of the way the wreck occurred, papa said he was not surprised, as he had known an instance of the master of a vessel who with his mate had got drunk, and who had managed to take his vessel to the south of Jersey, while all the time he fancied that he was among the Scilly Islands.（A Yacht Voyage Round England by W.H.G. Kingston）
英文を前から読んでいくために、語句のかたまりを作ります。こんな具合に課題文をスラッシュ（斜め線）で区切ります（スラッシュリーディング）。語句のかたまりを意識すると、リスニングで英語の意味をつかむのが楽になります。
When speaking of the way the wreck occurred,／（主語が文頭にないときの主語の前）papa said he was not surprised,／（接続詞の前）as he had known an instance of the master of a vessel／（関係代名詞の前）who with his mate had got drunk,／（接続詞の前）and who had managed to take his vessel to the south of Jersey,／（接続詞の前）while all the time he fancied／（接続詞の前）that he was among the Scilly Islands.
語句のかたまりを前から訳していきます。
When speaking of the way the wreck occurred,
その難破が起きた経緯について話しているとき
papa said he was not surprised,
自分は驚かなかったと、お父さんは言った
as he had known an instance of the master of a vessel
彼がある船の船長の例を知っていたからだ
who with his mate had got drunk,
航海士と一緒に酔っ払った
and who had managed to take his vessel to the south of Jersey,
そして、どうにか船をジャージー島の南方に進めた
while all the time he fancied
その間、彼はずっと思っていた
that he was among the Scilly Islands.
自分がシリー諸島の海域にいると
When speaking of the way the wreck occurred, papa said he was not surprised, as he had known an instance of the master of a vessel who with his mate had got drunk, and who had managed to take his vessel to the south of Jersey, while all the time he fancied that he was among the Scilly Islands.
When speaking of the way〜 → 接続詞＋分詞構文の形です。「〜するとき」
who with his mate had got drunk, and who had managed〜 → ２つの関係代名詞 who が先行詞 the master of a vesselを修飾しています。
お父さんは、その難破が起きた経緯について話しているとき、ある船の船長の例を知っていたので自分は驚かなかったと言った。その船長は航海士と一緒に酔っ払い、どうにか船をジャージー島の南方に進めたが、その間ずっと、彼はシリー諸島の海域にいると思っていたという。
When speaking of the way the wreck occurred, papa said he was not surprised, as he had known an instance of the master of a vessel who with his mate had got drunk, and who had managed to take his vessel to the south of Jersey, while all the time he fancied that he was among the Scilly Islands.
今回の課題文は少し長いですが、構成ははっきりしています。
・When speaking of the way the wreck occurred, → この文章の導入部です。「その難破が起きた経緯について話しているとき」
・papa said he was not surprised, → 文章の骨格（中心部分）です。お父さんは「自分は驚かなかった」と言いました。
・as he had known an instance〜 → ここから文末まで、「驚かなかった」理由が具体的に述べられています。
動画の後半部分でリスニング用音声が流れます。
