Watermarks exist mostly to deter casual, low-effort image theft, someone right-clicking and saving a photo to reuse it without credit, rather than to make removal technically impossible for a determined person with editing skills. Understanding that distinction shapes how to place a watermark effectively.
Placement matters more than most people assume
A single small watermark tucked into a corner is trivially easy to remove: crop it out, or use a basic clone-stamp tool if there's detail nearby to sample from. A watermark placed across the center of the image, over meaningful visual detail rather than empty sky or plain background, is much harder to remove cleanly, because removing it means reconstructing detail that's actually complicated to fake convincingly. Tiling a semi-transparent watermark diagonally across the whole frame, a common technique for stock photo previews, makes removal require reconstructing the entire image rather than patching one small area.
Watermark Image supports positioning and opacity control, letting you place a mark over the subject rather than defaulting to a corner, and tiling it if the use case calls for stronger protection, like a preview image you don't want reused before purchase.
Opacity is a trade-off, not a pure security setting
A very faint, low-opacity watermark is easier to blend away with editing tools, but a very bold, high-opacity mark makes the image less pleasant to look at and less useful even for its legitimate purpose (like a portfolio preview meant to still showcase the work clearly). The practical sweet spot is usually a semi-transparent mark, visible enough to clearly indicate ownership and complicate simple cropping or cloning, without making the underlying image unusable for its intended preview purpose.
Why no watermark is truly unremovable
Modern AI inpainting tools, the same technology behind object-removal features, can approximate plausible detail underneath a watermark, effectively guessing at what the covered area probably looked like, similar to how AI upscaling invents plausible new detail rather than recovering lost information. This means a sufficiently motivated person with the right tools can often produce a watermark-free version that's imperfect but usable. A watermark's realistic goal is raising the effort and skill bar high enough to stop casual reuse, not providing an absolute technical guarantee, legal recourse (copyright registration, licensing terms) remains the real protection against determined misuse.