Why closing Zeebrugge mattered to amphibious plans

How did the British propose to get around the Western Front's trench stalemate?

Amphibious landings in Belgium or on Germany's North Sea coast offered a route around the front. Restricting German operations from Zeebrugge would help protect the supporting ships.

Amphibious landings offered a proposed way around the Western Front's trench stalemate. The discussion considers landings elsewhere in Belgium and on Germany's North Sea coast. German submarines and torpedo boats operating from Zeebrugge could threaten the ships supporting such operations. Making the port unusable would reduce that threat and improve the position from which a landing could be attempted. These are proposed operations and their naval prerequisites, rather than landings that actually took place.