Raising juvenile Chinese fire bellied newt aquatic?

I'm wondering, can you raise juvenile fire bellies to be aquatic? Whenever I try to put him in water he'll always just swim away to the nearest land.

Also, what age would he be if he was about 4-6 cm?

Cheers
Zac

Is this a newly-acquired newt from a pet shop? Impossible to tell the age, but being that small he may still be a juvenile. He will eventually be aquatic, but it's hard to say when. Have you found some food that he will eat on land? See: Caudata Culture - Frequently Asked Questions

Correction: He is 4.5 cm long, roughly.

Uh, yeah I bought him from a pet shop around a month ago, he was relatively smaller, probably around 3.5-4cm.

They stated they were roughly under a year old, lol.

Yeah, I've fed him little cubes of frozen blood worms, that I obviously melt first then hand feed him, helps me bond with him more. He's been an awesome newt overall, considering most pet shop- bought newts don't eat for a while until they've gotten used to the new environment.

I've heard somewhere that the New Zealand climate is quite good for Fire bellied newts, that must be the case.

Mmmm..i´m quite surprised they are selling such small C.orientalis...i´ve never seen any for sale that weren´t adult.
With that size, it should still be a juvenile, which means that it will most likely be completely terrestrial until it reaches maturity. (beware!! juveniles CAN drown)
You can tell if a newt is in terrestrial phase because the skin will be slightly granular, hydrophobic, and not shiny. If so, you can keep it in a small tupperware with moistened kitchen paper towels(unbleached) as substrate and a couple of hiding places (pieces of bark for example). That will allow you to monitor it.

Also, you really need to improve that diet. Bloodworms are good, but they are not nutritionally complete, and if fed as an staple they can lead, over time, to dietary deficiencies. The base of a healthy diet should be earthworms! They are calcium rich, VERY nutritious, and caudates simply love them, they are the perfect newt food. However, because variety is always better, you can complete the diet with the bloodworms, with frozen artemia, waxworms, isopods, daphnia, tubifex/blackworms, small crickets, tiny slugs....

When it reaches adulthood, then you can follow the recommendations i gave you by PM for a suitable aquatic tank.
Bare in mind that even a healthy, aquatic newt can refuse to use the water if it´s not in adequate conditions, so make sure to check if the animal has skin adapted to water or land.

Good luck, this is a fascinating species