Thank you Valery, DA and JT.
JT, I would still use the lens, though I was switching between 24-70 and 70-400. The reason I would carry the lens is that the distance maintained between our boat and the ship.
For example the following one would not have been enjoyable without the 70-400. Not very often one gets to see two ships passing by so close. The FL was about 180mm. Though there is a bit of dead space to left, I felt providing a context made more sense and since I had 42MP, could easily crop.
A crop of the ship to the left. I doubt I would have gotten same quality with 24-70 heavily cropped.
Or a "mule" getting hitched up.
On the other hand, this would have been difficult without a wider angle lens. 24-70 at work here.