While none of these are called "Seaman's" hats, they are of the same type. I have made both the London Beanie and New York, and my guys really like them:

http://www.geocities.com/joyjannotti/seamanhatpattern.html

http://www.knitting-and.com/knitting/patterns/hats/london-beanie.htm

http://scrumptiousliving.wordpress.com/scrumptious-patterns/new-york/

I just want to thank you so much for the pattern. I have hunted high & low for this. Again Thank you!!!!!!

if you crochet also, there is a nice one that I've made from Lion Brand. I really liked the variation for the scarf pattern

Here is a link that might be useful: Seaman's Hat & Scarf