Constructed in around 1700, it's nine storeys deep, with the last two levels underwater.(它建于1700年左右，有9層樓深，最后兩層在水下。)

Underwater cities will provide more space.(水下城市將提供更多的空間。)

Whales carefully conserve their oxygen when underwater in a couple of ways.(鯨魚在水下以幾種方式小心地保存它們的氧氣。)

Astronauts practice spacewalks underwater in a huge special swimming pool.(宇航員在一個巨大的、特別的游泳池里進(jìn)行水下太空行走的練習(xí)。)

But underwater film-making wasn't that unusual, was it?(但水下拍攝電影也沒有如此不尋常，不是嗎？)

Underwater exploration is so much cheaper than space flight.(水下探索比太空飛行便宜多了。)

That hurts the ancient wooden poles holding up the city underwater.(這破壞了水下支撐這座城市的古老木桿。)

If the water's cloudy like that, it'll be hard to see anyone underwater.(如果水渾濁成那樣，就很難看得到水下的人。)

Was he like an innovator with underwater photography too?(他在水下攝影方面也是一個類似于革新者的存在嗎？)

Seals breathe air, but that doesn't stop some of them from sleeping underwater.(海豹呼吸空氣，但這并不能阻止它們在水下睡覺。)