▁Lake ▁Chap ala , ▁and ▁is ▁the ▁largest ▁and ▁most ▁important ▁fresh water ▁lake ▁in ▁Mexico , ▁account ing ▁for ▁about ▁half ▁of ▁the ▁country ' s ▁lake ▁surface . ▁The ▁lake ▁acts ▁as ▁a ▁reg ulator ▁of ▁the ▁flow ▁of ▁both ▁the ▁L er ma ▁and ▁Santiago ▁R ivers . ▁There ▁are ▁a ▁number ▁of ▁season al ▁and ▁sal ty ▁la kes ▁linking ▁to ▁form ▁the ▁Z aco al co - S ay ula ▁land - locked ▁system . ▁There ▁are ▁other ▁smaller ▁la kes ▁called ▁C aj it it lán , ▁Say ula , ▁San ▁Mar cos , ▁and ▁At ot on il co . ▁D ams ▁include ▁the ▁C aj ón ▁de ▁Pe ña , ▁Santa ▁Rosa , ▁La ▁V ega , ▁T ac ot án ▁and ▁Las ▁P ied ras . ▁J alis co ' s ▁surface ▁water ▁accounts ▁for ▁fifteen ▁percent ▁of ▁the ▁surface ▁fresh water ▁in ▁Mexico . ▁ ▁In ▁ 1 9 8 7 , ▁four ▁be aches ▁in ▁J alis co ▁were ▁designated ▁as ▁federal ▁marine ▁t urt le ▁san ctu aries : ▁El ▁T ec u án , ▁Cu itz m ala , ▁Te op a ▁and ▁Play ón ▁de ▁M ism alo ya , ▁with ▁an ▁extension ▁of ▁. ▁Play a ▁Maj ah uit as ▁is ▁ ▁south west ▁of ▁Puerto ▁Vall arta ▁with ▁a ▁rug ged ▁coast line , ▁numerous ▁in lets ▁and ▁out cro ppings . ▁The ▁C añ on ▁Sub mar ino ▁under water ▁can y on ▁is ▁located ▁off