I have evaluated this further -- an outside pond that abutts the house with a sealed glass panel on the house wall is pretty straight forward, with a) sealing the glass and b) joining the liner with the wall being the most critical tasks.
Pond extending into the house can be a lot trickier. In addition to the above:
-- there will be an opening to get into the house, by either animal (such as a beaver), insects, or human. What problem can this have?
-- air pressure change may cause water level to change but there should be plenty of air holes around the house.
-- How does this affect house insulation?
