Ship detection from aerial image
I have used Laplacian of a gaussian filtered image with sigma value of 3.
I have thresholded the LoG image with a high-pass filter.
I have used gray closing morphologic operator.
I have filtered the blobs according to their area.


There are several more ways to do it depending on the images, conditions(sea), illumination, ships etc.
For this image, non-color methods are preferable as shadows are not always predictable.