JSFiddle - React, Tailwind, and code Playground

HTML

<div class="image">
    <img src="http://placehold.it/350x350" />
    <div class="watermark"></div>
</div>

<a id="getPos" href="javascript: void(0);">Get Position</a>

CSS

.image {
    position: relative;
    width: 350px;
}
.watermark {
    width: 50px;
    height: 50px;
    background: red;
    position: absolute;
    top: 100px;
    left: 140px;
}

JavaScript

$(function () {
    $(".watermark").each(function () {
        $(this).draggable({
            containment: $(this).parent(".image")
        });
    });
    
    $("#getPos").click(function(){
        var imgPos = $(".image img").offset();
        var wmPos_tmp = $(".watermark").offset();
        
        var watermarkPosition = {
            top: wmPos_tmp.top - imgPos.top,
            left: wmPos_tmp.left - imgPos.left
        }
        console.log(watermarkPosition);
    });
});