Navy shipboard AC electrical systems are ungrounded for that very reason. You can inadvertently ground any one point with no mishap whatsoever. But one point only.
Those systems have ground detection circuits built in, to alert the crew of an inadvertent ground, so it can be cleared before some other point becomes inadvertently grounded.
However - there is some coupling between the floating electrical system and ship's ground that occurs because of the ground detection circuitry, and additional coupling that occurs due to capacitance. One can receive a severe shock, fatal even, by coming in contact with an ungrounded system "Hot" and the ships hull (which is all around, by the way).
But that hazard aside, while the electrical system floats, you can still ground any single point you like in the electrical system and nothing will happen.
