Wi-Fi as in 802.11a,b,g is pretty much not available. It takes direct line of sight access. For anything really long (more than 100 yards) beyond that it takes a directional antenna to a fixed location. It''s just not going to follow you around sailing well at all.
Wireless from say Verizon is possible in some areas to some serious distances. It''s a nice fast speed for about $80 / month. At the dock you should be able to get DSL or cable if available in the area.
Out at sea SSB radio is still slow and a lot of gear to buy.