According to posts on other boards,such as RCGroups, the ETNZ needs a LOT of work to make it into a good go-er.
I've just been playing with a second hand TT Victoria, and having sorted the rigging out to pretty much what the instructions say, it makes a really well behaved boat with good predictable handling in a wide range of conditions. Its 30" long and will sit in the rear footwell fully rigged (OK I have a Scenic, but theres lots of headroom left over) and weighs less than 5 lb.
Lots of good reports about the Graupner Micro Magic as well.
If your pond is liable to weeding, consider something with a fin with internal ballast, rather than a bulb, like the Fairwind.