To put your feet up means to relax, especially by sitting with your feet supported above the ground.
I like nothing better than putting my feet up after a hard day at work!
You work so hard. Come on, sit here and put your feet up!
Don't confuse with to find your feet, which means to become familiar with a situation or a place.
I'm new in town. I need time to find my feet.
According to the British Synchronised Swimming website, competitive swimmers must be extremely fit, and completely at home in the water. When tested and compared with other Olympic athletes the results showed that synchronised swimmers ranked second only to long-distance runners in aerobic capacity.