Sailor's hat is an item that must be worn during the Catapult Construction quest to convince Thaki the delivery dwarf that the player is a sailor. It can be obtained by searching the Drunken Sailor outside The Rusty Anchor pub in Port Sarim.
If lost, a replacement hat can be obtained by searching the
Drunken Sailor again.
This hat is almost identical to a Customs hat, obtainable in Rocking Out. However, the Customs hat cannot be kept and is a darker shade of blue.
There's a man in east Falador wearing what appears to be a magenta sailor's hat. In a court case it is revealed that his name is Ikis Krum.
Jossik from Horror From The Deep also wears the aforementioned magenta sailor's hat.
Ellena, the farmer by the Catherby fruit tree patch, also wears a tan coloured sailor's hat.
Morten Holdstrom seems to wear a red version of the sailor hat.