An interesting concept, but there would be several issues relating to placing a hotel underwater in a lake.
First, the logistics of moving supplies to the lake and having divers provide the construction which would be quite costly. Also the building supplies would have to be resistant to water damage. Plus the facility would have to be air-tight with backup safety systems, all of which is quite expensive.
Secondly, most lakes lack the proper water current to keep the water clear enough to allow the underwater views that the patrons would be seeking. Without proper water circulation, algae and silt would form over all of the facility. This silt and algae would deteriorate the building and make maintenance quite expensive.
There are several ocean underwater hotels, since the ocean has more currents and flowing water. But I do not know of any under-lake hotels, but there may be some in lakes with strong water flow.