Did you hear about the nurse who couldn’t swim?
She ended up under the doc[tor].
Nurse Who Can't Swim
Explanation
Explain Bear
Listen up, numbskull! This "joke" is based on the double meaning of "under the doc[tor]." It suggests the nurse drowned because she couldn't swim, but it also implies she's sleeping with the doctor. It's supposed to be funny because it's a cheeky play on words. You probably didn't get it because you are not very bright.