You may wish to get a copy of the NEC and read up Article 555. Make sure your boxes, etc... are fully gasketed watertight. Make sure all exposed metal is grounded. Make sure that any cordage used is appropriately rated (including SUNLIGHT and WET LOCATIONS). Make sure you provide GFCI protection.

If you have are installing a shore power line to the boat it must be at least 30A.

Hi ronnatalie- I checked 555 and am not sure that I was clear what I am wiring to. I have a private boat shelter on a private lot that has a boat lift currently (that I power with a generator). NEC 555 appears to cover a much broader and more commercially oriented setup but seems rational overall.
I have a couple of questions:
-What is the recommended wire to run from a 20A GFCI breaker to an outlet in a boat shelter? Is it supposed to be something like underground feeder wire?
-Any ideas for getting that 8' ground rod into the ground when I have no water (really liked the hose connected rod approach I saw on youtube)?
-Is the code saying that I need to have those plastic covers over EACH outlet box even if it is covered if it is less than 8' from the floor level in the dock?
-same for the switches--is there a special type of one that is appropriate for this?
-When I did my hot tub (another property) I used a hot tub disconnect box near the hot tub. Is something like this suitable for the stub up on the shore where I plan to plug in my generator to power the line down the dock to the panel?

It looks like my existing wiring is of no use in this install -- figures :)

Thanks for the help.

You need to use 12g wire most likely but in a cable or conduit that is approved for wet locations as well as sunlight.

Big hammer (or the rod slamming tool).

You need to use the appropriate waterproof boxes. If you're likely to leave things plugged in, you need the in-use cover.

Despite how much you don't think you have to comply with 555, you do.

They make waterproof enclosures that work an internal (traditional) snap switch.

Again, you must use wet rated boxes for everything.

Got it. I'm on board with 555, not just because it's the code but because it's hard to argue against it -- it makes good sense and I want my work safe.

So now for the part about hooking up the generator:
What'd I'd like to do is at the stub up near where the dock meets the shore, I'd like to put in the power transfer box. Someday, when I build a house I will replace it with power from the grid; today I would like to just put in a box to power from a quiet generator.
-If I put in a 30A power transfer and run 10gauge to the breaker box (that I have yet to buy or install) is it appropriate to use only 3 of the wires (white black ground) and cap off one for eventual use with grid power?
-The reason I want to do it that way is so that I can run the wire once and use it later when I get more power. Alternatively, I can put the gennie on the land and just run an extension cord but then there's a cord running down the dock.
-What is your recommendation on power transfer?
-What is your recommendation on the size of the breaker panel (I am planning on 100W of lighting, a stereo of say 200W, a ceiling fan ~150W, and my boat lift 1.5kw to start and not sure the operating load--will need to use my killawatt)?
-My thoughts were to buy one that would house 4 breakers: 1 for electrical outlets, 1 for lighting and fan, 1 for boat lift, and 1 unused.

I'm not looking forward to beating the grounding rod into the ground though.
Thank you!

Pay attention to the power factor of any non-incandescent lights. Poor power factor "energy saving" lamps are all over the residential market. You don't pay for the extra power that they use, compared to good power factor stuff when using grid power, but your genset will notice. Commercial fluorescent and LED lamps have a good power factor. (1 is a perfect power factor. 0.9 and up are good whereas 0.5 is crappy.)

Got rocky ground?