Careless Driving Rear-ender Hydroplaned

The question is did you drive according to the road/weather conditions? Rearend collisions in itself do not constitute Careless Driving.

The term "due care" has to be looked at here. Attempt to explain to your self as to why this collision occurred (besides wet road and poor driving conditions). If your answer goes along with what any other reasonable and prudent driver would have done in the same situation then you have a good defence and should have a trial. Otherwise consider resolution.

Going by your story, you should be able to go back to that intersection and take some pics or video next time it is raining.

Due to the seriousness of the charge though, legal representation would be advisable.