Although sea travel doesn't effect me personally just yet with only having chars on the FEI I'd nevertheless still like to recommend an excellant book on the subject if I can, as while it's somewhat of a sizable tomb (heck it seems nearly all those I find myself ending up getting are.
) it's content, both in scope and detail, more then make it well worth the read.
Rose, Susan - Medieval Naval Warfare 1000 - 1500