From my years of keeping these I found that Nepenthes generally don't like to be submersed in water...in saying that I have kept both N.alata and N.ventricosa submersed and they have done swimmingly. Mind you I do keep mind in a greenhouse or in my very hot and stuffy 1 bedroom unit.
The Sarracenia pitchers ("Ground" pitchers) can do well being submersed, I have had several different species outside and most of them have flowered.
Of the Drosera (Sundew) species I have kept, most do well sitting in water baths and I can say the same for Dionaea muscipula (Venus fly trap).
Utricularia (Bladderworts) like to be very, very wet and there is an aquatic species but not sure if it's is in or allowed entry into NZ??
Keeping CP is like keeping fish, somethings work well for others but can epically fail for others. And plant shops and CP collectors will often have differing ways of doing things, but whatever works for you. And that's my 5 cents worth.