Second Bermuda Triangle in the Pacific?

So, my moving container was supposed to arrive in Australia the day before yesterday, but apparently, the ship is delayed by 7 days. It isn't a big deal and I am not familiar with the operation of a ship, but how can a ship suddenly be late? And when I say suddenly I mean that, apparently, the captain - who has been at sea for four weeks at that point - only finds out about a 1-week delay two days before the scheduled arrival date. Being completely unfamiliar with maritime navigation, I assume that you know your starting point, you know your end point, the distance between the two and your average speed - should be pretty straightforward to figure out how long it takes (give or take a day or two). And, failing that, it should be possible to figure out any possible changes in the arrival date way ahead of time.

As I said, it's not a big deal, I'm mostly just curious as to the inner workings of the shipping industry.

On a more annoying note, this means that I have to spend at least another seven days on the air mattress - I am so sick of it by now (it's been over 3 weeks), I can't wait to sleep in a REAL bed again - not to mention the fact that my apartment is still essentially empty, and the emptiness and echo are starting to get really old.

At least I finally got my driver's license and a credit card (applying for them required documents I received only recently - namely, a printed payslip and a utility bill) - well, technically, I don't have either yet, but I have a temporary license and an approval-note from the credit card issuer, so in a couple of days, I should have both, taking one more step back towards normality. I also submitted a lease-application for a car, so hopefully, in a week or two, I will have my own set of wheels again...