But water in caves doesn't only erode. 可是洞里的水不光只是侵蚀
which are only a few centimetres across. 而它们的巢窝相隔不过几厘米远
Bats are not the only commuters in these Bornean caves. 蝙蝠并非婆罗洲洞窟中的唯一常客
Yet these depths were first explored only two years before man landed on the moon. 然而人类直到登月前两年 才第一次进入这个深渊
an inner world where only the most adventurous dare to go. 一个只有最勇敢者 才敢涉足的地底世界
are only found in the lower courses of their rivers. 都是位于河流的下游地段
including the world's only fresh water seal. 包括世界上唯一的淡水海豹
Here, only the narrowest line separates life from death. 在这里 生与死只有一线之隔
the rivers are not only a vital source of drinking water, 河流不仅是唯一能解渴的重要水源