Make sure it's clean river sand, not beach sand.

确保那是干净河沙，不是海滩的沙子。

youdao

They believed that the ankh could control the flow of the river and make sure that there was always enough water.

他们相信十字勋章可以控制河流的流动，确保总是有足够的水。

youdao

If you swim in a river or lake, be sure to investigate what is below the water surface.

如果你在河里或者湖里游泳，一定要弄清楚水面下有什么。

youdao

It says it has carried out comprehensive environmental studies to make sure any impacts on the river are minimised.

BBC: Drought fears after low winter rain levels

Sure, there is the river in between, which is a barrier.

WSJ: A Diplomatic Breakthrough

"This will help to make sure people can continue to enjoy the river ready for the start of this year's spring and summer boating season, " Mr Watts added.

BBC: River Nene: Silt removal aimed at improving navigation