ok, squirt details: Pump from Cornwall model boats, 2.2l/min at 10v, mine runs on 7.2v, perfectly ok for this use. Action switcher and esc. Plumbing is silicon tube and connectors from pets at home, (aquatic section!).
The only thing to think about with the pump is that its not positive displacement, so has to be below the water line to prime, easy with these hulls.
Ian