I have a Scuba, my folks have a Snorkel. All pricey, but worth it! The snorkel is 3 feet high and made for a deep redwood or cedar tub. The scuba is made for a 2 foot deep stock tank, so my tub is an old 6ft stock tank wrapped in Reflectix insulation, surrounded by redwood slats and benches so it looks classy.
Both stoves come with a wooden fence to cover the stove so you don't toast your buns on it. The snorkel will burn ANYTHING at a roar, with the Scuba I have to be a bit more selective and use only dry wood, in smaller chunks. Both stoves really need to burn at a roar to get a decent heating time. My Scuba goes from spring water temps (COLD!) to 105 deg F in about 4.5 hours, on about 3-4 armloads of wood. If its' already lukewarm, it's hot in a hour on one armload of wood. I use a submersible pump to circulate the water, otherwise it stratifies with hot on top. My Dad uses a canoe paddle to stir it. A cover is essential for good heating time, I use floating blueboard insulation panels.
Both stoves have a minimum water level line clearly marked....let the water get much below this, and you'll warp/melt the stove.
Great customer support from the Snorkel Stove Company too!
DANF