I like to keep a few different measuring devices nearby no matter what it is I am working on. 12 inch combination square is essential and versatile. It can check for square which is a must for good work. I use it to set saw blade height and router bit depth, and for marking lines off of an edge for hole placement.
6 inch ruler, handy for checking thickness and smaller measurements. For woodworking you want one that is graduated 8ths, 16ths, 32nds, and 64ths, although I rarely use 64ths. Can also be a combination square and I use one like that often but not a necessity with the 12 inch also, but for small layout can be easier to handle. For these two it is good to have etched graduations so they do not come off. Accuracy is important so I only use a quality brand for woodwork. Boat parts you can use a cheap brand but for cabinets and furniture you will get into trouble.
18 inch flexible ruler, flexible because the boat is all curved and it can take the shape for laying out things. This one came from Staples and had cork on the back which sticks to fiberglass better. Used mainly for drawing lines on the boat and layout. The graduations did not start at the end however which is a bad design. Grind away so that the end is the beginning of the graduations and it is more useful.
12 foot tape measure, this is the perfect size for 98% of all tape measuring, especially woodworking. No need for a giant tape that is hard to hold and klunky. I use this all of the time for measuring parts and cutting up rough boards. There are longer tapes in the shop that rarely get used, for bench work and general tasks, 12 ft is the way to go.
These four are a good start to any shop and you will find that there are more to be had that can be of help, larger squares of different sizes are nice, also a few longer levels will come in handy at some point.