State the most suitable data type for the variables waterTemperature and systemLog used in the algorithm below.

stationID ← USERINPUT
waterTemperature ← 18.5
systemLog ← "Normal operation"
criticalAlert ← "CRITICAL TEMPERATURE WARNING"

waterTemperature ← USERINPUT
IF waterTemperature > 30.0 THEN
    systemLog ← criticalAlert
    OUTPUT systemLog
ELSE
    IF waterTemperature < 5.0 THEN
        systemLog ← "Low temperature warning"
        OUTPUT systemLog
    ELSE
        OUTPUT systemLog
    ENDIF
ENDIF