Airports are expensive, reinforced runways etc..
Here is an idea: instead of runways, use 10foot deep water (or antifreeze in winter) and build planes without landing gear and tires/brakes.
This will prevent fires on crashes, so no firetrucks needed too.
Also saves on cost/weight/maintenance of landing gear/tires, which are prone to failure sometimes.
The saved weight could go to extra ranged and or reinforcement required for water landing.
Also now flying over the ocean is less dangerous, so some flights may route more direct.
Also for unplanned landings, there may be more suitable water bodies than runways for aircraft.