Translation of "Imprudent" in Japanese

It is very imprudent to swim in the rapids.

この急流で泳ぐのはとても無謀なことだ。

I was assailed by the stupid, but unshakeable, idea that if I was imprudent enough to move my hand I'd be noticed.

下手に手を動かすと気付かれてしまうという強迫観念が俺を襲う。