Being on the water means prolonged exposure to sun, wind, and rain. The proper boat top can extend your cruising time by protecting you from whatever Mother Nature dishes out. 
Top Terms
Boat tops (often called canvas, in nautical-speak) come in all shapes, sizes, and colors—and depending on your personal preferences, you can opt for a simple sunshade to a fully enclosed arrangement, complete with windows and doors.
The most common kinds of tops are made of canvas fabric with a collapsible aluminum framework—kind of like a convertible top on an automobile. Put the top up when you need it, fold it up and stow it when you don’t.
Bimini Tops
Bimini tops (or biminis) are usually stand-alone shelters, connected to the boat by the top’s frame. A bimini goes up quickly, and provides welcome relief from the sun. However, because a basic bimini is open on all four sides, it does little to fend off wind or driving rain.
Convertible Tops
The front edge of a convertible top snaps to the boat’s windshield, while the top’s frame typically attaches to either side of the boat. Although a convertible top blocks the sun, wind and rain can still sneak in from the sides and back.
Variations on a Theme
Let’s take the concept of your boat’s canvas a bit further. A bimini or convertible top is adequate for fair weather, but if you go boating in spite of the meteorological conditions, you may want to think about expanding your boat’s usefulness with more canvas.
Adding canvas with clear (plastic or glass) windows (aft and side curtains) to a top goes a long way in keeping the wind and rain off of you. Just zip the aft and side curtains to the boat’s canvas at the top, pop the bottoms of the curtains into snaps on your boat, and keep on boating.
A top with aft and side curtains is called a full enclosure. Depending on your boat and the way you use it, you can choose either a sit-down enclosure (the most common) or a stand-up enclosure for more useable space and headroom.
Camper Canvas
In addition to a full canvas enclosure for the front seat area, you can include a canvas camper back to shelter the passenger area from the windshield to the transom. A camper back usually has plenty of headroom and windows to prevent claustrophobia from closing in. As you may have guessed from its name, a camper back is great for overnighters—keeping not only the rain and wind out, but insects as well.
Canvas Care
Over time, your boat’s canvas is going to collect its fair share of bird droppings, dust and dirt. When washing the top, be gentle—use only mild detergents, rinse well with fresh water (not salt water), and allow the canvas to dry thoroughly before stowing the top.
Be extra careful with the plastic windows, because the see-through material is soft and easily scratched. Use a clean, soft cloth, mild soap, and lots of water to wash the window panels.
Well Worth It
Although investing in high-quality canvas might seem a bit pricey at first, with proper care, it’ll look good and add value to your boat for years to come.