I agree it was not demanding I did it 9 something at like with an RPE of 7ish. I think it's important to note that is done without fins. For GUE professionals the standard is raised to 600yd in 14 minutes.For reference, a PADI DM must swim 400 yards in less than 12 minutes, so that is like 300 yards in less than 9 minutes. 14 minutes for that distance does not seem very demanding.
Does the padi standard allow the use of fins?