Upon further look freeze framing, what looks to be a boat could just be a coincidental wave (don't see a boat), the initial fireball seems to come from the passing truck (and the debris seems to point that direction as well). Leaning more to this being the truck at this point.but could still be a boat.
What is 100% certain however is that Ukraine has confirmed this was their doing and was a very well planned attack at a critical junction.
https://twitter.com/user/status/1578628414197485569