The complexity and cost of dealing with stowaways has increased dramatically. Together with increased illegal immigration and related human poverty the problem seems to increase.

As with any other event, prevention is a lot better than treatment. For your guidance you should look at the following measures to assist you in the prevention of stowaways:

• The Master should discuss with the agent the extent of risk arising from stowaways trying to board the ship and the methods used
   
• Keep updated on stowaway situation in area of port of call. IMO produces quarterly reports on stowaway cases
   
• Do not trust that the port can fulfill its responsibility for adequate safety
   
• The pilot ladder should be hoisted inboard immediately after the pilot has left
   
• Anchor chain hawse pipes should be covered and secured in position
   
• The Club has been made aware of several cases concerning stowaways hiding in ships' rudder housings and the opening should be restricted in size to prevent access
   
• Rafts used for painting should be retrieved on board upon completion of daily work
   
• Deck stores should be locked
    
• A vigilant and continuous gangway watch, if needed supplemented by local watchmen, should be maintained throughout the whole period while at anchor or in port. (Any extra cost will still be cheaper and easier than having to deal with a stowaway problem)
   
• The gangway should be hoisted when port workers and visitors leave the ship - particularly for periods at night when it is not in frequent use
   
• Arrange a pass system and tally all visitors
   
• Access to accommodation should be limited to only one or two doors and others locked. (Ensure that they can be unlocked from the inside to enable escape in an emergency)
   
• Whilst at anchor, the lookout should be doubled up at night or during reduced visibility and there should be frequent deck patrols
   
• Cargo or other lighting should be rigged to shine outboard whilst the ship is at anchor
   
• The lookout should treat approaching small vessels and boat as a craft that may be carrying intruders. All means available on the ship should be used to prevent people boarding the ship from such boats. The port authority should be immediately advised of any attempt at boarding
   
• Use random security patrols to look out for people in unusual areas and to check locks and seals
   
• The ship should be searched before sailing. For many vessels a thorough search is not practicable but at least a check of unlocked storage areas and the lifeboats should be made. Remember also that any unsealed containers are a common concealment. Some ships may find it helpful to compile their own search checklist. A more extensive search may be conducted on the outward passage to the port entrance or sea buoy

You can find more information in this IMO guideline.