I always like amphibious aircraft like the Martin Seamaster.
They have rescue and patrol capabilities that exceed those available from any other type of aircraft. I think that it might be time to revive the concept for both civilian and military purposes. I am not saying to bring back the Seamaster, but to develop a fully modern aircraft with comparable capabilities. One thing that I think might help would be a pneumatic outer hull for the part in contact with water - essentially a huge air-filled tire, with separate inflation of many individual cells. This would ease the battering caused by landing and taking off through waves.