In the mid 1950s, Tom Cooke of the OPAS brought waterbombing back on track by developing float-mounted roll-top tanks that allowed water to be dumped in a deluge rather than a trickle to combat fires. A cockpit lever controlled dumping and lights notified the pilot when the tank was filled. The system was so successful that by 1960 all 35 Beavers and 8 Otter of the Provincial Air Service had been fitted with the tanks. The Otters were also fitted with larger belly-mounted roll-over tanks.
Eventually the external rollover tanks were replaced by built-in float tanks. In 1971 the OPAS converted 7 Grumman CS2F-1 Trackers antisubmarine aircaft into land-based waterbombers with fuselauge tanks.
IN 1961 Canadair of Montreal began design of the CL-215. This aircraft was purpose-built as a waterbomber from the outset with large internal water tanks and a sophisticated dropping system.