he's obsessed!!

my almost-four-year-old (he'll be four this august) is completely infatuated with sprinklers.

we live in an apartment complex, and every night at a certain time, the sprinklers come on along one large grassy strip. we're talking about at least ten sprinklers here, some big, some little, some spinning, some stationary ~ i.e., all quite different. one is supposed to spin and doesn't because it's stuck. one is cracked but not broken.

anyway, whenever it's warm enough still at night, i take my son downstairs to play in the sprinklers. he LOVES them. he's enthralled. he's heartbroken on the nights when we can't go out and play in them. he sets up pretend sprinklers in his room and makes sprinklers out of blocks, old margarine containers, ring toys... he tells me what the different kinds of sprinklers are, what sounds they make, and what they do when they turn on and off.

one thing i've noticed lately (and i was amused about) is that when i take him downstairs, he'll run around and play in the water for just a couple of minutes, then spends the rest of the time squatting in front of the sprinklers, just watching. he goes from sprinkler to sprinkler, back and forth among all of them, squatting for seriously minutes at a time, just watching.

my SO noticed this afternoon that our son had made an accurate model of a sprinkler.

is this normal for his age? do other kids have similar obsessions?