悪水[akusui] undrinkable water
井戸水[idomizu] well water
一衣帯水[ichiitaisui] (being separated only by a) narrow strip of water
一水[issui] current (of water)
溢水[issui] inundation

飲水量[insuiryou] amount of drinking
飲料水[inryousui] drinking water
烏の行水[karasunogyouzui] quick bath
雲水[unsui] itinerant priest
塩化水素[enkasuiso] hydrogen chloride

枯淡[kotan] elegant simplicity
淡い[awai] light
淡黄色[tanoushoku] pale yellow
淡紅色[tankoushoku] pink
淡彩[tansai] light colouring

淡水[tansui] fresh water (i.e. not salt water)
淡雪[awayuki] light snowfall
濃淡[noutan] light and shade
濃淡画像[noutangazou] gray-scale image
平淡[heitan] simple