Chickens do not swim upwards when on slabs

System.getProperty('os.name') == 'Windows 10'
System.getProperty('os.version') == '10.0'
System.getProperty('os.arch') == 'amd64'
System.getProperty('java.version') == '1.8.0_25'
System.getProperty('java.vendor') == 'Oracle Corporation'
System.getProperty('sun.arch.data.model') == '64'