In Kuwait, ice is not a luxury. It is the first line of defence for your catch and for the quality of the whole day. Summer deck temperatures pass fifty degrees, and any fish left on deck for half an hour loses value fast. The real question is not whether to bring ice, but how much and how to pack it.
A workable rule: one kilogram of ice per kilogram of fish for a single day out at the height of summer, less in winter. Ten kilos of fish needs at least ten kilos of ice, and more if the box is old or the trip is long. Ice is far cheaper than a lost catch, so do not skimp on it.
Cubes melt slower but leave air gaps and chill the fish unevenly. Crushed ice contacts the whole surface and cools faster, which makes it the better choice for fish boxes. Slurry ice, a mix of ice and salt water, gives the fastest cooling of all because the liquid carries cold into every gap, and it suits large fish like kingfish and grouper.
If you go with slurry, bag the fish first or use a box dedicated to it, because salt water soaks the flesh and softens it. One safety note: never reuse meltwater or ice from the box as drinking water afterwards.
Opening the lid every few minutes for one more fish, parking the box next to the engine or in direct sun, and laying a warm fish on top of the ice instead of burying it. Each one raises the internal temperature and shortens the life of your ice. If meltwater pools in the box, drain it at once, because water speeds the melting of what is left.
Do not drop a sun-hot fish straight onto ice and hope for the best. Bleed it, rinse it in clean seawater, and let it cool in shade for a few minutes before it goes in the box. That small step saves a lot of ice and gives better flesh. Check sea state and wind before you launch as well, because a windy day usually means a shorter run and different ice use. The B7R app puts sea state and seasons on one screen.
Empty the box on ground away from the sun, wash it with fresh water and soap, and let it dry open. Salt and fish smell stay in the corners if you rush it. Same for knives and cutting boards. If a fish sat warm for hours or smells off, do not eat it and do not give it away. Proper cooling is cheaper than a hospital visit.
Plan before you load the boat: how much ice, which box, where it sits. The B7R app is free on Google Play and keeps tide times and sea state in one place: https://play.google.com/store/apps/details?id=com.q8dm.b7r