Ice is one of the foremost items on the boater's mind. Unless you own a large yacht with a full-size refrigerator or have an icemaker on board, one of the first items on
your list of things to bring aboard is always ice. Whether it's to keep perishables fresh, drinks cold, bait from rotting or to put the "clink" in cocktails, the boating experience would be greatly diminished without ice.

The Melt Down
Ice is only useful, though, if you can keep it frozen until needed. Once taken out of the freezer, the longevity of ice depends on many factors: its size, shape, density and temperature. It also depends on how you use the ice, since various applications require different ways of handling and storing the ice to maximize its intended benefits.

It's easy to think of ice as having a temperature of 32 degrees Fahrenheit, since that's the point at which (pure) water freezes, but ice that's fresh from the freezer is much colder than that, usually at zero degrees or lower. Zero-degree ice is hard; it has a nice musical ring to it when it drops into a glass and has more energy stored in it than ice that's closer to melting, which is soft, watery and drops with a dull thud. Therefore, the colder ice will cool your drink more quickly than its warmer form, which tends to melt before getting the job done.

Ice Picks
The longest-lasting form of ice is a solid cube with six sides equal in area, because it has the least surface area per volume. A thin chip or slab of the same volume would have a greater surface area, and therefore release its energy and melt more quickly. A cube with a hole through it (as dispensed by many ice machines) is the worst form of all and will melt in a hurry. In air, this means that one shape will transfer its energy, get warm and melt more quickly than another. In liquid, an equal volume of ice of a given temperature will cool the drink equally, regardless of its shape. The critical difference between the shapes is how long the ice lasts without refrigeration after it's taken out of the freezer. Solid cubes win, but are difficult to obtain unless you're willing to make them in ice-cube trays at home. The half-moon shape produced by many automatic home icemakers is a distant second, but it's still better than most commercial bagged ice.

Because of its extreme mass, block ice lasts a long time, but beware of a subtle difference. Much of the so-called "block ice" available at marinas is actually chipped ice that's been mechanically compressed into block form, so it's more porous and less dense than ice that's been frozen as a solid block. The compressed form won't last as long, but is quicker, easier and less expensive to manufacture. If you have a home freezer, you can make the real thing in large plastic storage containers.

Freeze On
Getting the most from your ice involves making a decision about the manner in which you expect to use it and the corresponding method of storage. If you're going to use ice in a cooler to keep drinks cold, the most efficient way of transferring its energy to the bottles and cans is through water, which is a much better thermal conductor than air. Let the ice melt into ice water, draining it off only when its level rises too far for convenience. The ice will melt quicker, but it'll also do a better job of cooling your drinks.

On the other hand, if your aim is to preserve ice efficiently for later use, it should be kept out of the water, because air is a better insulator than water. Double-wrap it in sealed plastic bags with drain holes punched in the bottom to let any water out, and store the ice on a shelf or on top of other items in the cooler. If your boat has a built-in refrigerator - even a small one - you can ensure your end-of-the-day libation is a cool one by storing a small bag of cubes in its freezer section to get cold while you're underway. If you're cruising in an area where ice supplies may be unavailable, bring an extra inexpensive Styrofoam cooler to store a long-term ice supply. It can be sealed and stored below - out of the sun - and since it won't be opened and closed constantly like your primary cooler, the ice in it will remain cold much longer.

Cooler Than Cool
It also helps to be careful when buying a cooler. They're not always equal: Better coolers will have thicker walls to provide more insulation. Avoid coolers that are any color other than white (or stainless steel), as darker colors tend to absorb heat rather than reflect it.

There are also some measures you can take to help your cooler perform better. If possible, keeping it out of direct sunlight is a big step. In warm climates, draping a reflective thermal "space blanket" over it will also help keep internal temperatures from climbing, especially if you can provide an airflow space between the blanket and the top of the cooler. Otherwise, keeping a (white) cushion on top of the cooler will not only help insulate it, but provide additional seating as well. Another trick is to place an internal insulating panel on top of the items in the cooler before closing the lid, or you can use a simple piece of construction foam board cut to fit for the job.

Don't overwhelm the cooler by filling it with unnecessary warm goods. Besides perishable food items, it should only contain what you'll need for the next 12 hours or so. When you first stock it, bring items that have already been refrigerated. On extended trips, replenish the cooler first thing in the morning, while the new items
are still at the temperature of the previous, cooler night.

And when making decisions about where you should store items in the cooler, remember that the coldest spot will always be at the bottom.
The result of being careful about how you handle and store your ice will be that you're more likely to have it around when you need it, which can only add to the enjoyment of time spent on your boat. How cool is that?