Yes, "too" close by definition would be a problem. But even a meter of water between you and the source absorbs 99.994% of the radiation (down to 6 thousandths

Yes, "too" close by definition would be a problem. But even a meter of water between you and the source absorbs 99.994% of the radiation (down to 6 thousandths of a percent vs in air, or by a factor of about 1/16000).