Fire is a risk with any car. However, it is far down on the list of "things that can harm me involving my vehicle". So far down the list that frankly, I don't care, ICE or EV, about the risk of fire.
As far as the physics of it, Kia battery packs are sealed very well, and inside those packs, you will find very well sealed polymer cases containing the actual lithium batteries. Salt water isn't getting to them. Tesla on the other hand has the batteries placed in foam, with the contacts accessible, inside the case. If the case leaks, whatever leaks in, has access to actual batteries. Over time...
This is why almost all of the fires after floods are Tesla, and not cars with architecture like my ev6, or the Volvo, or other similar module case within case designs.
More risky, is a fuel rail above hot headers in a wreck. But i never worried about that either to be fair.
I inherited my mother's car, which is an older Buick. I drive it and keep it for reasons completely unrelated to any mechanical aspect of the vehicle.