I see.
Now, Imagine if I was pulling 6 PWM outputs of 30ma each and 6 20ma continuous digital outputs at 12 volts, worst-case scenario.
That would give a power dissipation of at least ((13.2-8.2)0.30) + ((13.2-8.2)60.20) Joules, the power used by the Arduino not-withstanding.
Now that, in an underwater container most likely to be immersed in potting epoxy, probably wouldn't be a good idea, would it. I wonder what the most temperature sensitive component on a Due is.
Maybe I should just order a ATMega and make a RBBB. Anyway, thanks for the response.