Вот что мне ответил один из операторов - может кому пригодится:
Normally there is not a lot of activity at hte lagoon around this time, it is already to warm for
Ice cave tours which are very popuplar during the winter.
But still not warm enough for the lagoon to be ready for boat tours.
There are still many other things in the surounding area, Skidoo tours, jeep tours, glacier walks and climbs.
I suggest you check out
https://visitvatnajokull.is/Тем не менее, если все же кто - то предоставляет такие услуги в марте - буду благодарен