I spent over 15 hours on sailing and killed two 5 stars monster/ghost ship and I got 2 COMMON Chests only. Actually, I found the chance of getting a chest and other rewards is MUTUALLY EXCLUSIVE. I never see that I can get a common chest with other things at a time. I think it is fine to get a chest only if it is a UC chest or at low lever monster/ ships ( say 3 stars or less). However, it should not applicable to a high level monsters/ships. If I get a common chest from a high level monster/ ship, it should provide another reward other than UC chest at the same time regardless the amount. This is my suggestion.
