I'm all at sea.我是一片茫然。

all at sea 好形象

例句：

1.I'm all at sea; I've no idea how to repair cars.
我手足无措，不知道怎样修理汽车。

2.My new hi-fi has so many lights and switches that I was all at sea when I first tried to use it.
我新买的那台高保真音响设备有许许多多指示灯和开关，以致我第一次打开它时竟不知所措。