Why early Cold War planners tested jet flying boats

What was the logic behind jet-powered flying boats such as the Saunders-Roe SR.A/1 and P6M SeaMaster, rather than using aircraft carriers?

They offered dispersed water basing and over-ocean flexibility during an era when nuclear attack seemed likely to make fixed runways dangerously vulnerable.

The Saunders-Roe SR.A/1 and P6M SeaMaster belong to a period when planners explored many competing ways to operate jet aircraft. Water basing offered options around small islands and to countries without carriers. Early jet reliability also made the possibility of an emergency sea landing attractive. Nuclear attack gave dispersal another purpose: aircraft operating from water might remain usable after conventional airfields had been destroyed. The wider argument is that postwar experimentation narrowed as military requirements and ideas about conventional warfare became more settled during the 1960s.