hello,i just installed my new garmin fishfinder but i do not have a windshield to protect it from water splashing on the back of it.somtimes here in galveston bay it gets very choppy real fast and waves have broke over the front causing water(salt) to splash all over.will this hurt it untill i get back.they claim it is water tight.how should it be cleaned i.e. sprayed off?thank you