The Sea Kings were wating around FI for more than 2 years just to have a few panels screen time. :ninja:
If they're actually 5000 kilometers like Oda says then yes, that could be very possible, because obviously they could move from place to place with little trouble.
He may just be portraying them at their current size (smaller than 5000km) so that he can even include them in the panels, they have cool designs.
Just like he made the Shichibukai "bigger" for their introduction spread at the Marineford War.