I'm sorry, you're wrong the way most people are wrong about this. If you believe in the Buddha's existence, or Gandhi's or Napoleon's, you believe the same way I believe in the Flood, with even less justification I'd say,...
How so? The evidence to support the justification that Napoleon existed is overwhelming. Several independent sources from various countries can confirm the existence of Napoleon. There is no evidence to support the claim that a global flood drowned our world.