in one's element

昨日ジョッギングの途中荒川の河口付近の土手から久しぶりに富士山が見えました、もっとも5時を過ぎていたので富士山といっても影ですが、くっきりと綺麗な形でした。
さて、スウェーデンの漁師町を満喫する夏の旅行を題材にしたReader's Digest ９月号の記事 Sweeden's Perfect Seasonからの抜粋です。
Sliding across the rain-slicked deck, careening into each other, Marcus and I managed to toss back all the traps. Martin, meanwhile, stood firm and smiling at the wheel, secure in his element.
"Jan alskar sommraren!" he shouted to us, flashing a grin as a monster wave crashed over the hull.
"element" は要素、成分の意味だけではなく、これまでにも "the elements" (5/7/2016)と "trace element/mineral" (4/6/2015)を取り上げましたが、上に出てきた "in his element" はまた違う意味を持っているようです。辞書を見ます。
・Wiktionary: In a situation which is entirely suitable, familiar, or enjoyable.: You can tell he's completely in his element when he's talking about his favorite hobby.
・The American Heritage Idioms Dictionary: In an environment naturally suited to or associated with one; doing what one enjoys. For example, He's in his element when he's doing woodworking. This term alludes to one's natural abode, as does the antonym, out of one's element (used by Daniel Defoe in Robinson Crusoe, 1719: “When they came to make boards ... they were quite out of their element”).