You need to check the cargo aboard the ship.
Playing as Suzy:
Enter the bar and talk to the barman. Ask for a drink and order a water. He’ll give you a bottle of SPRING WATER. Leave the pub and go down the ramp. There’s a mooring ROPE. Pick it up and use the bottle with water on the sea to change the spring water into SALT WATER. Go back up again and give the water to Alec.
Climb the ladder at the front of the building to the platform and take the ANCHOR from the sign. Then climb the ladder further to the roof. In your inventory, combine the anchor with the rope and wait for Alec.
Playing as Alec:
Enter the pub and talk to the barman. Aks for the drinks and order a BEER. In your inventory add the salt water to the beer. Talk to the crewman and greet him. Ask if he’s a sailor. Ask if he’s been sailing long and reply surprised. Then tell him he doesn’t look like a sailor and when he wants to know why not, tell him about his drinking. He’ll prove you otherwise.
Leave the conversation and offer the crewman your beer. He’ll give you an EMPTY MUG. Then talk to him and ask him to show that trick again. The salty beer will be gone in no time and so will the crewman be. Take the JACKET from the chair and the HAT from the table. In your inventory combine the hat with the jacket to wear the uniform and give the empty mug to the barman. Leave the bar and walk to the plank onto the ships doorway.
Playing as Suzy:
Use the grappling hook on a porthole and you’ll hang on the side of the ship. Enter the top porthole into the captain’s cabin and take the CARD, the ENVELOPE and the INK PAD from the table. Leave the room through the porthole again and lower yourself to the porthole below. It’s locked but when you use the birthday card on the porthole you’ll flip the latch and you can enter the bunk room.
Walk to the stairs on the far right to go one level down. In your inventory use the ink pad with the envelope and put the envelope on the floor. Then use the door to knock and get the attention of the crewman. He’ll pick up the ink pad and put it on the table.
Playing as Alec:
Take the ENVELOPE from the table. Use the ink pad on the mug and wait for the crewman to drink.
Playing as Suzy:
Use the stairs on the right to go one level down and knock on the door again. The crewman will answer again, this time there’s nothing.
Playing as Alec:
Use the keypad next to the security door and look at the smudged keys. Press them all followed by enter. You can now walk to the stairs. Go all the way downstairs to the crate with the dollar sign on it and wait for Suzy.
Playing as Suzy:
Go all the way downstairs and use the top crate to remove it. Then you’ll find out what’s in the bottom one.
Game source: A copy of the game was found here on the internet.