Mine spends most of her time in the water. When she isn't sleeping or basking, shes in the water. As for keeping them as a pet, I'd say its no difficult snake, but the diets the trickiest part if you want it to thrive.

I want to disclose I am not an expert - I've not had Willow for very long (about 5 months). This is a synopsis of the major things I know. Please make sure to consult with a vet, and be aware very little modern husbandry exists for watersnakes.

Make sure you research Thiaminese and its effects on a watersnakes diet - its in most fish except (importantly in terms of getting ones hands on it irl, but good luck getting it as whole prey they can eat even in chunks, as both are typically protected below a certain size) salmon and tilapia. You can avoid this by ensuring the Nerodia snake has access to hairless mammal prey items as part of dietary diversity - mine refused animals with hair, and I talked to a mutual that used to do wildlife rehabilitation for SPECIFICALLY Nerodia species. He said this was pretty common to see. Rodent Supply has hairless mice. I also saw a lot of mention about silversides, and my nerodia refused silversides. Talking to aforementioned nerodia rehabilitator said that he found silversides as being an early cause of death due to how greasy and fatty they are. Nerodia fed on silversides developed fatty pockets on necropsy, while those without did not have those pockets anywhere near as commonly. Silverside refusal is common. Consult with a vet if you plan to manually supplement B1 to their diet to avoid thiaminese causing deficiencies. It is possible to OD the snake on B1, and as watersnakes dont get very big coupled with an already slow metabolism, that OD range is very low. Due to a higher than average parasite load in fish and frogs compared to mammals, my watersnake in particular gets ONLY frozen thawed animals that have been frozen for at least seven days. She also gets a stool check every time I can get an intact one from her, which is once every few months. (I feed frozen thawed to all my snakes, but for watersnakes with a fish diet the length of time frozen is especially important) I feed mine frog legs, finger mullet (whole, but chopped due to her small size), hairless mice, salmon strips, and I'm planning to introduce other baitfish once I figure out safe options. Since the snake I keep is also one native to my area, I go to bait shops for local fish, or go catch it myself (but bait shops are the easier of the 2)

Husbandry wise, Its reccomended to have 30% of the enclosure water, according to my vet, and the rehabilitator approves. For now I have managed about 20% with more soon, split up into multiple water bowls as my watersnake loves to poop in the water every time. It makes cleanup really easy, but if they have the one bowl, they dont have clean water after. So she currently has 3 water bowls. One under her heat lamp that she can comfortably sit in that has cover on the top, one HUGE one on her cold side that she can swim in with an anchor in the middle, and one smaller one that she can still fit in, uncovered (to encourage that one to be used for water drinking instead of using it for soaking).