Complex sentence: It is possible that the formation of the fleet was broken in heavy weather or fog, but after seven weeks at sea the proximity of the Irish coast made landfall there attractive for the purpose of taking on supplies and effecting repairs.
Split into simpler sentences: It is possible that the formation of the fleet was broken in heavy weather or fog. But, after seven weeks at sea, the proximity of the Irish coast made landfall there attractive for the purpose of taking on supplies and effecting repairs.