關于 across 與 through 的基本用法區別，請參見：www.hz123456.com/Article/200810/544.html 　　

至于與 sea 和 desert 搭配，用 across 和 through 均可，但意思有所不同：　　

Kara’s home was a long way off across the sea. 卡拉的家在大海對面很遠的地方。（摘自《朗文高級英語詞典》）　　

A trawler is a fishing boat that uses large nets that it drags through the sea behind it. 拖網漁船就是指拖著很大的網捕魚的漁船。（摘自《牛津高階英漢雙解詞典》）　　

The grandiose scheme for a journey across the desert came to nothing. 不切實際的穿越沙漠的計劃已成泡影。（摘自《牛津高階英漢雙解詞典》）

The car broke down when we were driving through the desert and it took us two days to repair it.  我們駕車橫越沙漠時，汽車壞了，花了兩天才修好。（摘自《牛津英語語法》）

Kara’s home was a long way off across the sea. 中的across the sea 表示“在大海對面”；　　

A trawler is a fishing boat that uses large nets that it drags through the sea behind it. 中的through the sea 表示魚網在大海中拖過，此時的大海被視為一個“立體”的東西（想象一下在大海中拖魚網的情形）。　　

至于across the desert 與through the desert，有時可混用，其細微差別是：若說話者把 desert 視為一個“平面”（比如這片沙漠比較平坦），則可能用 across the desert；若說話者把 desert 視為一個“立體面”（比如這片沙漠起伏比較明顯），則可能用 through the desert。