"I was thinking of something more like an ice cube, running between two ice walls - but, there." He tapped a fingertip a little fondly on one of the fish suddenly cluttering up his sketch. "That's a step simpler, even. Good." Anything that didn't require developing an entirely new polymer with properties hitherto only found in the more esoteric plastics was on the more feasible side of things. He set his chin in his hand and watched the sea life multiply, absently finishing off his half of the bagel, considering safety measures. Emergency-release gelling agents - built-in brakes and water damage prevention - but a possible suffocation risk, and a clean-up nightmare. Steam cushioning; potential for boiling people alive.
Again, details. He was happy to leave those to the people who had a knack for the finishing flourish. "And your way has disappearing bikinis." He took the pencil gently back, and added another set of columns below the growing illustration. "Flooding's easy enough to prevent; an emergency valve into the river or the reservoir is simple stuff. It just leaves you with the little problem of how not to break people's necks. But there's always a trade-off, isn't there, to getting in on the ground floor of innovation." He pursed his lips together, a not entirely successful attempt to conceal a smile. "So to speak."