Big chunks of the coastline in Wales are crumbling away and at risk of flooding over the next 100 years, the National Trust has warned.
The charity controls more than 143 miles of the Welsh coast but said more than 70% of it was under threat from rising sea levels and increased storms.
It includes really beautiful areas, like the dunes on the Gower Peninsula where part of Doctor Who was filmed.
The trust wants more to be done to deal with the impact of coastal crumbling.
If their predictions come true, beaches will disappear and coastal footpaths will have to be moved.
Rising sea levels are caused by the planet getting warmer because of greenhouse gas emissions, causing water to swell and polar ice to melt.
Within the next 100 years, some experts have predicted that sea levels will rise by a metre and climate change will lead to more severe storms.