I live on the west coast of Western Australia so early mornings are always the best time to photograph boats as the sun is behind me, the water is blue and the strong sea breeze is not chopping up the water. Always choose a sunny day so use a weather app such as Weatherzone and your SunriseSunset app to work out the best time. If you are shooting both the interiors and the exteriors of the boat start with the exteriors as the light will be better. Shooting the interiors is not such an issue with the light as the boat can be repositioned to suit the orientation of the room you are shooting.
There are a couple of ways of capturing the boat in action and at the same time the exteriors. Do your research and find a vantage point that is close to where the boat is moored like a beach, a jetty or a groyne. Consider what is in the background behind the boat will be and where the light is coming from. Have contact either by phone or 2-way radio with the skipper and get them to cruise past with the boat at different angles - going straight across from left to right and right to left, then diagonally coming towards you and away from you from both the right and left. that way you will get all angles of the boat. This is where your telephoto lens will come into play - I use a 70-300mm with the camera on burst mode, around f4-5.6 to keep the shutter speed up, ISO 400 for the same reason and a continuous focusing mode eg AF-C or AI Servo.
The second way is with a drone - my DJI Phantom 4 does the job well with both video and still capabilities. Make sure you shooting in RAW and 4K and use a variety of video techniques such as panning from different angles, tracking, overhead and alongside the boat. The advantage of using a drone is that it can be done at the same as the still interior shots with the boat out of the mooring on the river or ocean rather than two consecutive shoots where the boat has to pick you as photographer up after you have shot the boat from a distance.
The degree of difficulty in shooting boat interiors lies in how big the boat is. I have photographed everything from huge multi-million dollar catamarans with large bedrooms, bathrooms and living areas that are bigger than most people's homes, to tiny boats that you literally have to crawl onto the corner of the bed to get the shot or to shoot the bathroom (often not much bigger than a cupboard) without getting yourself or your camera gear in the reflection.
The main rules are firstly to take off your shoes on boarding, to make sure you have rubber tips on the legs of your sturdy tripod (both are to prevent scratches to the wooden floors) and finally to have the boat out of the pen and in open water so you don't have to photoshop out other boats and pens from the window and deck views. It may take a bit more effort from your crew but it will save your client a lot of money in time in post-production.
Most boats have lots of shiny, reflective surfaces so I rarely use a flash - the only time I would use my powerful external Canon 600EX-RT flash would be to help balance the internal & external light in a large living or external covered deck with views. Like with real estate or architectural photography I mostly use my wide angle 16-35mm lens, ISO 100, f 11 to show the overall space using all the tricks of the trade to make those spaces look expansive eg not showing where the room begins and ends. Try shooting from straight on as well as from the corner - all ensure you are 'telling a story' with each image including showing how one room links to another. Bathrooms in boats are particularly challenging but don't forget that, unlike in real estate photography, both a vertical and horizontal format can be used. Once I have shot the 'overall picture' I then change lenses to my 24-105mm f4 lens and hone in on the detail using a shallow depth of field- the steering wheel, nice tap ware, handrail details etc.
Like with real estate & architecture photoshoots you need to shoot at least a couple of angles of every room and more in the kitchen, living room/s and main bedroom. You will also need to shoot the wheel house or bridge, details of the navigation instrumentation, the cool-room if there is one and the engine room - for some reason engine room details are very important to a potential buyer if the boat is being sold. I would suggest you shoot this at the very beginning of the shoot or at the end once the boat is back in the marina as engine rooms are very cramped, hot places!
It is important to declutter all areas - take most things off bench tops, get rid of tissue boxes, take shampoos out of the shower recess, turn on all cabin lights and bedside lamps ... to make the areas seem larger and add to the 'clean-line' look you are after.
Most boats have externals decks. Now I am not a boating girl (and you don't have to be to photograph boats) and I actually had to look up the official names for these areas which need to be included in your photoshoot if the boat has them - bow deck (front), stern deck (back), flying deck (upstairs), cockpit, helm and swim deck. Take images both looking out from the deck (to also capture the view and give perspective) and back in towards the boat from both straight on and across-angle directions. Also include the boats name in the shots and details of anything interesting - fishing rod holders, the tender, stainless steel fittings.
if your images are to be used for marketing purposes eg the boat is for sale or will be available for hire, it is good to include lifestyle type images in your photoshoot. Ideally have a couple of good looking models (male and female) lounging on the decks with cocktails on hand or at least a platter of food arranged in the foreground of a deck scene. Colourful cushions and a beach towel thrown over a deck chair look great as does fluffy white towels and quality soaps in the bathrooms and coffee table books scattered in the living room or beside the main bed.
Boat shoots are always fun and if you know what you are doing and get great images you will be invited back again and again ... the feeling of warm wind blowing in your hair whilst looking out to azure waters as you cruise back to the pen after nailing the photoshoot is hard to beat!