the idea behind image re-sizer is to have one main image that will be resized based on the fly based on the width and height tags used in the image tag.
soo using:
<img class="WADAResultThumb" border="0" src="<?php echo $row_WADAboats["dt_boatImageThumbnail"]; ?>" alt="<?php echo $row_WADAboats["dt_thumbnail_alt"]; ?>" width="100" height="100" />
would automatically create a new cached image using the 100px width and height specified.