In the game you collect resources from your resource generator buildings, and from islands (apart from attacking). The resources from the captured islands are gathered to you via some resource boats (one for each resource).
The longer you wait, the more resources the boats give you. What is the capacity of this ships?
According to the Boom Beach Wiki:
These boats can fill up. The capacity of a boat is equal to the combined sum of all your Resource Bases of that Resource type's collectors' capacity. Basically, if one of your Resource Bases' collector fills up, you will have to collect from the boat for that base's collector to start producing again. This means that overall Resource Base production slows down after a few hours (because the lower-level Resource Bases fill up with resources) and stops eventually.
The boats/ships do not have a capacity limit but every island you lose, the amount of resources in the boats/ships will be decreased.
Here's the answer if anyone is still looking for it (from I think I finally cracked the case of resource boat limit! — Reddit /r/BoomBeach post by PixelPerfect41):
Info:
I only have 1 resouce base Production: 210/hour Cap:1450
I collected my resource boat before leaving the game for weeks
I didn’t get attacked during this time period
What happened:
When I came back to game after a few weeks I was greeted with 1450 wood
After checking again about 30 mins later I saw the second image the boat started to increase again
My theory:
Every resource base has its own limit. When you login to the game you collect resources from islands to your boat. And just like tapping your resource production building they get emptied. Boat is capless but resource bases are not.
Trivia:
The longer you wait the slower your production will get because low level production buldings will start to fill up
That explains why don’t get infinite loot when you quit the game for years
