When I did the Tokara trip you normally leave your tackle bags at the back of the boat and with the rough sea the bags are basically underwater most of the time. I was using a Shimano Deck Bag which I enjoyed using but after day one the bag had about 15cm of water in the bottom. I've also tried the Shout bag, North Face and HPA bag but these have all leaked in one way or another as I think they are soft bags and good for traveling and storing but because they are soft they tend to lie in all different positions with the zip in the water or on the deck, also you don't always zip them 100% and lastly hooks, knives, etc tend to put a few holes in the bags.
I have now been trying and using the Shout Jigger "Box" which has been great and because the zip is off the deck and there is a small lip at the top of the box seems to work a charm. I have watered this box down to test on the boat and at home along with putting the box in the line of fire in some rough conditions with water coming onto the boat and no water inside yet. I also saw in Japan the guys using a box from Shimano which was bigger and worked well. One issue is traveling but if you have a big trucker roller bag it fits inside or use it for carry one luggage with all your reels (minus spools) etc.
Cheers,
Nick