One of my favourite cycle rides is to Pevensey in East Sussex. Along the coastal path there are a few of these:
Martello towers, small defensive forts built around the time of the Napoleonic wars, can be found all along the South Coast. They stand up to 12m high and generally had a garrison of one officer and 15–25 men. Their round structure and thick walls of solid masonry made them resistant to cannon fire.
Turning off the sea path is the Bay View Park a fantastic holiday homes and camp site right on the beach: https://bayviewpark.co.uk/
Eastbourne has a thriving fishing industry: http://eastbournefishermen.co.uk/about.html and cycling back through Sovereign harbour the fishing boats were moored up for the night: