All across the seabed offshore there is a clear record of the ice disappearing and the sea flooding in between 19,000 – 16,000 yrs ago.
This is shown by the transition from subglacial sediments to glaciomarine sediments
Eventually fully marine conditions were re-established offshore and throughout the Holocene (the last 10,000ys) our coastline began to take the form we see today.
Roberts et al., 2019:
https://doi.org/10.1002/esp.4569