We did work on large (80m) boats for 5 years. Most of the AV concepts used on land apply onboard, but you will have other associated technologies you will need to learn and apply. SeaTel or other sat tracking systems, VSAT and 3G terminals (if you do IT), SATB, serious power management issues.
There is also heavy certification and procedures you need to follow to comply with the stringent insurance and safety requirements.
Those things aside, working on marine products is a blast with lots of travel, fun people and a nice income stream.