After slowly groping I have exceeded the time the "shipyard guarantee" of 50 cm depth in approximately 1.50m deep pool rigorously and consistently to be able to determine without any damage. Due to the good controllability by short spurts, it can maneuver properly in the bath. Hovering is quite possible here too short commands the whole secret. The depth control might be a bit slower, more sensitive.
Unfortunately, my boat was quite vertrimmt, so that pretty much had to be installed by the Tarierschaumstoff under the nose; also it emerges only to the top of the tower from the water, the cover does not come free. And unfortunately it heeled greatly when using the rear thruster (right / left), which looks very unnatural. But that is no other way in the deep attachment of the jet vane.
When functionality Graupner but thought along: In low battery aboard the submarine is eventually no longer be controlled; when it reaches a certain threshold, the plunger then moves to the home position "emergence", so that the submarine by itself comes back to the surface.
Back home, followed by a "technical analysis": The charging station is built so simple that you can also be installed without major problems a hollow female connector for a 9V power supply, and so forego near a wall outlet where the expensive rechargeable batteries; I use to an old power supply of a defective Gigaset telephone. Observe the polarity and remove batteries, or a battery switch / power supply installed (alternatively: jack with switching contact)!
When the charging plug is a normal Graupner BEC plug (Modellbauzubehör) with an applied reverse voltage protection in addition, so that you probably could invite the submarine directly to a model with NiMH charger program. However, one should be able to limit the charging current to low values, and pay particular attention to the polarity.
But must be clear that in such activities lost any warranty!
What Lubricate the shaft affects how Graupner recommended in the manual, with me transparent silicone grease has proven that you can attach a paperclip sparingly (!). A lot about the size of half a pinhead is sufficient perfectly, and leaves no traces of oil in the garden pond or swimming pool. Ballistol should not better use, because this forms an emulsion with water.
By offering an optional cable for model chargers, and / or by delivery of the charging station with a standard socket for a power supply Graupner would significantly enhance the model with little effort and can distinguish it from "disposable toy" the same price range effectively.
Still, fun 100%!