Well Bob and Chris,,
wind is by my experience much more the problem for container ships than waves/sea, special close to ports
or inside ports when the vessels moving slow. Why you think they use 4 tugs,,,because it is no big deal ?
I remember when we were only half loaded by draught and had 6-7 high empty containers on deck.
I once needed 1.5 hrs with 3 tugs to berth the vessel in Hamburg in 2006,,with force 5 winds !!!
That vessel was the ex CSAV Santos,,not really considered anymore a bigger container ship with "only" 2500 TEU
but you can believe me,,they behave like sailing vessels when slowing down and to keep them in control is a task and not "no big deal"
brgds
capt ted