Complex sentence: In contrast to Dublin, the settlement was abandoned, possibly because it lacked continuous access to the sea; the river tides would have made access to the water impossible for a number of hours per day.
Split into simpler sentences: In contrast to Dublin, the settlement was abandoned.It has been argued that possibly because of changing tidal patterns, it lacked continuous access to the sea. The tides would have made access to the water difficult for a number of hours per day.