I’ve never been stuck in a forest fire so I can’t speak from experience.

But I would run! Fires move fastest when pushed by a tailwind, so run in a cross-wind or head-wind direction. I’d keep my eyes peeled for water, then jump in, stay low, and breathe through my shirt to avoid the smoke. Once the fire sweeps through and burns out an area, I’d probably just stay there (since there’s nothing left to burn).