Tāmen zài dàhǎi zhōng chàngyóu, gǎnshòu dàzìrán de zhuàngkuò.
They swam freely in the ocean, experiencing the grandeur of nature.
Tips
memory
畅 means 'freely / unobstructed' and 游 means 'to travel / swim'. Together: moving freely with joy - think of a fish gliding effortlessly through open water.