From YT (I think they are serious):

The Iso-phone is a telecommunications concept providing a service that can be described simply as a meeting of the telephone and the floatation tank. By blocking out peripheral sensory stimulation and distraction, the Iso-phone creates a telephonic space of heightened purity and focus.

Only a couple of decades ago our primary means of telecommunication was the telephone box—essentially a designated piece of architecture providing a contextually neutral space for remote conversation, removed from the hubbub of the outside world. The Iso-phone takes these notions of context neutrality and environmental dislocation to their sensory extremes.

The Iso-phone creates a new kind of immersive telephonic space by removing the peripheral physicality of the world. The user wears a helmet that blocks out all unnecessary sensory input while keeping the head above the surface of the water. This water is heated to body temperature, thus blurring the boundaries between the user's body and the external physical environment. This combination creates a space which provides a pure, distraction-free environment for making a telephone call. The only sensory stimulus present is a two-way voice connection to another person using the same apparatus in another location.

Two working Iso-phone helmets have been built for experimentation and exhibition. They have been designed to operate in any body of water deeper than two meters. For the full sensory experience, two tanks have been custom-built, offering total control over the user's environment.