Marine insurance is rather a complex matter.
Policies are long and couched in language both colourful and obscure.
The relevant act is the Marine Insurance Act 1906. Pirates' includes passengers who mutiny and rioters who attack the ship from the shore, but 'thieves' does not include clandestine thefts by one of the crew or a passenger. The insurer must have an insurable interest , i.e. he must personally stand to suffer from the loss insured against. The interest must exist at the time of the loss, though it need not when the policy is signed. Gambling policies where the insured has no interest at any time are likely to be void.