"Again, we apologize for the rather utilitarian nature of the restraints, I know it's not very comfortable, but we'll be getting them off you shortly. This isn't some sort of torture chamber, you signed the paperwork, you're being well-paid. We just had to find a way to dip subjects efficiently from the other side of the protective glass. Not really a situation where we can ask you to get in yourself and ensure you stay fully submerged for just the right amount of time. You'll be fully out in a second, and the restraints will release, and then we'll need you to shower for...oh, at least twenty minutes in the cleaning chamber. Can't risk any of the stuff leaving that room.
If you want, you can start telling us how you feel, about any strange sensations or effects it might've had on your mind. More convenient if we can double up on procedure and assessment. Off the record, you turned out beautifully..."