It is possible to buy 100% cover for collisions from your hull insurers as well as extending the policy to cover collisions with other objects (known as fixed and floating objects cover).
It is also possible to purchase top up insurances to ensure that if the ship is completely lost, that the indemnity is adequate to actually replace the vessel. This type of insurance is known as Increased Value and is generally capped at 25% of the agreed value on the main policy to prevent over-insurance. War and Strikes in particular are actually perils which are insurable and will often be purchased as an extension to the main marine cover, which almost but not quite replaces the exclusion that will be found in the main marine hull policy wordings
