Photoshop :: High-Res Image - Use Blending Mode To Extract

I have a high-res image of a model of a ship that I'm looking to put on top of a seascape image. The pictures below are a lot smaller and cropped then actual.

Here is a crop of the image of the ship, luckily it's on a plain background and nothing more complicated: After much trial and error, Fluid Mask did a decent job and I'm on the fence about saying useable:

However, this is a thought I had when scrolling through blending modes on the ship's layer. Here it is on Multiply:

Obviously it's too dark, but in terms of the edges on the small details like the ropes, it looks great. I got thinking about somehow automating Photoshop to recognize wherever a pixel is different from the background layer below it, Photoshop would be able to tell where the image is and where the background is, since Multiply removes any white but leaves other colors (albeit darker).

I don't know how this would be done if it's possible at all, I'm guessing with some sort of code made into a plugin or something.