Today's industrial action at Liverpool Coastguard station is part of a week of planned disruption.
Staff plan to down tools again tomorrow between 11am and 12pm, with more strikes each day until June 15.
The Public and Commercial Services Union believes lives will be put at risk if the base closes.
Staff at Liverpool coastguard station are starting a rolling series of strikes.
They walked out between 3am and 4am today.
The station, which is based at Crosby, is one of nine the Government plans to close.