You guys amaze me - I can't think how much time yo must put into researching all these planes.. I've never even heard of them!

Let alone guess a rusty old photo!
Ben

It's an enjoyable challenge. Some are "easy" (definition - I KNOW I've seen it before but I don't remember where)
This one is a tad difficult, and the graininess of the photo doesn't help. In this case, there are several "clues" that led me to my first guess
- reasonably well shaped hull
- pusher engine mounted between the wings.
Assumptions:
- single seater (not too clear on the photo),
- high mounted fin/rudder/tailplane.
While this is "typical" of many of the early WW1 flying boats, it's characteristic of the Lohner/Macchi single seater flying boats
Armed with the now known fact that it is not a Type L Lohner/Macchi now I would have to concentrate on other details and compare ...
- shape of the auxiliary floats
- is that a biplane tailplane arrangement?
- squared off nacelle/radiator
- 4 bladed prop,
- two bay wing cellule
- wing cellule attached by struts to the hull.
This one is NOT easy.
Other assumptions - this is a photo of a real airplane and not some cobbled up composite;