On July 28, 2016, at 0111 eastern daylight time, JetBlue Airways as flight 1561, an Airbus A321, N913JB, experienced turbulence during cruise that resulted in one flight attendant sustaining a serious injury. There were no injuries to the other passengers and crew aboard and the airplane was not damaged. The flight was operating under the provisions of 14 Code of Federal Regulations Part 121 as a regularly scheduled passenger flight from New York John F. Kennedy International Airport (JFK), Queens, New York to Grantley Adams International Airport (BGI), Christchurch, Barbados. The flight diverted to Luis Muñoz Marín International Airport (SJU), San Juan, Puerto Rico . According to the operator, aircraft encountered turbulence during cruise while the flight attendant (FA) at position #4 was carrying a pot of hot water from the aft galley towards one of the aft lavatories. The FA stated that she held on to the galley counter with her right hand and swung the coffee pot in her left towards the jumpseat away from another flight attendant. She stated that the aircraft experienced another sudden drop and the water in the pot flew up in the air and landed on her left shoulder and left side resulting in second-degree burns. The flight crew indicated that at the time of the event the weather conditions were mostly clear, but had encountered short segments of instrument weather conditions as forecasted with no associated turbulence or precipitation. They indicated that they had been actively using the onboard weather radar, but there were no returns that led to deviations. The first officer stated that the turbulence was sudden, with no other associated rain or precipitation and then immediately calm again, so no actions were taken. The operator indicated that the flight data from the Quick Access Recorder (QAR) showed smooth conditions prior to the turbulence encounter.