There is one ferry operator that sails to the Isle of Man called the Isle of Man Steam Packet. They offer sailings from Liverpool and Heysham in England. Dublin and Belfast in Ireland.
Sailings on board the fast craft Manannan take from 2 hours up to 2 hours 45 minutes or the slower conventional ferry Ben My Chree take 3 hours 30 minutes. All sailings arrive at the Isle of Man Sea Terminal located in Douglas. From here the whole island can be easily accessed, with your vehicle or use public transport from the nearby by Douglas bus station.
Isle of Man Steam Packet: Belfast, Dublin, Heysham, Liverpool
If you are planning to travel from Europe by sea then first you will need to sail to England or Ireland. There are routes available sailing from Belgium, France, Holland, and Spain to England and Ireland.
STENA LINE: Rosslare (Ireland) to Cherbourg (France).
IRISH FERRIES: Dublin (Ireland) to Cherbourg (Ireland) and Rosslare (Ireland) to Cherbourg (France).
P&O FERRIES: Dover (England) to Calais (France), Hull (England) to Zeebrugge (Belgium) or Rotterdam (Amsterdam).
BRITTANY FERRIES: Portsmouth (England) to Caen, St Malo, Cherbourg, Le Harve (France), Poole (England) to Cherbourg (France), Plymouth (England) to Roscoff (France),
Portsmouth (England) to Santander and Bilbao (Spain).
DFDS SEAWAYS: Dover (England) to Dunkirk or Calais (France), Newcastle (England) to Amsterdam (Netherlands), Newhaven (England) to Dieppe (France).