i've heard that they can drown in water, but i had a small millipede fall into a 2 inch deep pond in my terrarium. no clue how long it was in the pond, it was slightly curled, lying on its side on the bottem of the pond motionless when i woke up in the morning. but later in the day when i came back, it was gone, haveing crawled back out again i assume. the little pede was only about an inch long.

