It should be "el agua".
"Yarda" is "yard", but only as a unit of measurement, not when it means land or garden. For that you have to use "patio", "jardín" or any other similar word; otherwise, it sounds like "There are many trees in the metre".
"Jugar Monopoly", is becoming mainstream in many places, but there are still countries where it feels incorrect. "Jugar al Monopoly" is considered correct everywhere.
The usage of time is a bit strange: you started talking about one specific day (un día en el lago) in the past, suddenly you are talking about several days ("muchos días"), and then you switch to present saying that "jugamos cuando es de noche".