in his element

Reader's　Digest 6月号の記事 "The Mariner vs. the Sea" からの引用です。

It's just past 8 p.m. on August 1.
Laurnt Camprubi is about 15 miles off the coast of northwestern Spain, hoisting the mainsail on the deck of the 39-foot sailboat Jeanne. Ever since he left Lisbon, Portugal, the day before, he has been fighting the elements. But he is in his element too.

"elements" は 5/7/2016 に取り上げていますが、最後の文にある "element" は別物ですね。
辞書を見ます。 慣用句で "in one's element" がありました。

・Merriam-Webster: in a place or situation where one is comfortable and does well: At school she was (really) in her element.
・Collins Dictionary: In a situation which is entirely suitable, familiar, or enjoyable.: You can tell he's completely in his element when he's talking about fossils.

1/18/2018には "brave the elements" も取り上げています。