Not every espionage is successful. On the one hand, the success rate is increased by every completed level
of espionage research, and on the other hand,
espionage attempts can be blasted if the enemy has a watch tower on the target isle, which gives him a chance of catching your spy and make him reveal his master (i.e. you, in this case).
A spy ship can only be used once. When the spy ship arrives at the enemy isle, you will receive a system
message which tells you if your espionage was successful or not, and - if the espionage is successful - you will
receive a spy report.
Preconditions for the construction of spy ship: