 Despite the overwhelming French majority in numbers , the attack was a disaster : nearly 1 @,@ 000 French soldiers were killed as the boats were caught in open water under the island 's gun batteries : several were sunk with all hands . Heavy fire from batteries and Royal Marines prevented a single French soldier from landing and the retreating fleet was subject to heavy fire from the smaller island to the north , inflicting further losses . British casualties were negligible . Although this operation indicated the probable result of a full @-@ scale invasion of Britain , the threat remained and British forces began a close blockade of the surviving landing craft that were anchored in the Cotentin ports . A month after the battle this strategy resulted in a secondary success when a French frigate and corvette passing along the coast were intercepted and defeated by the blockade squadron . 
