What the dish actually does
For a box turtle, the water dish is not just a drink — it is a bath he will climb into daily to soak, drink and very often pass waste. Soaking is part of how box turtles stay hydrated and keep their skin and shell healthy, and many drink most reliably while sitting in the water rather than at its edge. Outdoors, the same dish doubles as a cooling spot on hot afternoons, and many box turtles time their soak for the warmest part of the day. That changes what you are choosing: not a bottle substitute, but a small, safe pond he can get his whole body into.
Depth: chin-deep, never swimming-deep
Choose a dish wide enough for the turtle to sit in completely, with water no deeper than his chin where the lower shell meets the neck — box turtles are land turtles and poor swimmers, and a deep bowl with steep sides is a genuine drowning risk for an animal who tips in and cannot climb out. The sides should be low and gently sloped, and sinking the dish into the substrate until its rim sits almost level with the ground removes the climb altogether. A rough stone placed as a step helps smaller or older turtles in and out.
Material: heavy, plain and unglamorous
Weight is safety here: a heavy ceramic or stoneware dish, or the glazed saucer sold for large plant pots, will not tip when a turtle levers himself over the rim, and its slight roughness gives his claws purchase. Thin plastic bowls slide, tip and get chewed at; tall moulded resin rock-pools look natural but usually have sides too steep for safe exits. Whatever you choose should survive daily scrubbing, because a fouled dish needs hot water and a brush after every use, not a rinse when you remember.
Placement and the daily routine
Put the dish in the warmer half of the enclosure but not directly under the basking lamp, where the water would heat and foul faster, and keep it somewhere level so it does not slowly tilt and spill. Expect to change the water every day — box turtles reliably soil their soaking water — and top it up on hot days when evaporation and bathing both draw it down. A second shallow dish of clean drinking water is a reasonable extra during hot spells. In winter, when indoor heating dries the air, check the level at night as well as in the morning — a dish that is empty by evening needs a top-up in the routine, not just a morning refill. Watch how he uses it for the first week: a dish he never enters is usually too high, too exposed or too cold, and each of those has a fix.
The refresh routine is simple but daily, which is exactly where households slip, so put it on his profile through KinsLe's Family Sharing — dish depth, placement and the daily change written down where every family member can see it — and the turtle gets the same clean, chin-deep soak whoever is on turtle duty.