The best place to admire the Galle coastline is from the top of the bordering Galle Fort. This ancient fort, which prevented the 2004 tsunami from hitting the Galle town offers stunning views of the waves hitting the rocks below.
The entire Galle coastline can be easily seen from the fort. In fact, a leisurely walk ensures that one can see different aspects of Galle from old Galle to fishing towns to lighthouses to beaches and many more. I am sure it is an even better sight during the monsoons when the seas are rough.