Lanun have the +1 food on sea tiles as part of their palace, but the -1 food for farms as part of the seafaring tech. they should be together (in which ever one, it doesnt matter) so that teammates don't just get the drawbacks (currently Lanun in team means others farms are crippled but they dont receive the benefit of +1 food water tiles).
In our multiplayer game Lanun was unable to build galleys with sailing tech, in either of my cities (both were coastal to two different seas, both could build lighthouses but neither could build galleys)
edit added: ok i checked it out and apparently neither had non-coastline ocean in them. but they are seas, not fresh water lakes. and if its big enough to make it cease to be a lake, it should be allowed to build boats (it lets you build a lighthouse if its connected to water thats not a lake). there was even a resouce in one of the seas (and i could build fishing boats, just not any other type of boat)
ideally you should be able to build lighthouses as long as you're along a lake, and you should always be allowed to build boats if theres a water tile next to your city. i had two fair sized seas that were length wise that i was looking forward to using boats in and transporting units around using my seas. but now it appears im hopelessly landlocked despite being surrounded by water and having the appropriate techs.