The nature of the offshore petroleum activity and the likelihood that both the tortfeasor and the claimant of a potential incident participate in the petroleum activity results in one of the most characteristic features of the petroleum contract, namely contractual regulation of liability. The allocation of liability is often based on the knock-for-knock principle which basically means that the parties assume responsibility for any loss or damage incurred to their own property as well as for liability to certain third parties. Liability for loss is assumed regardless of how the loss is caused. Through regulations providing for distribution of liability in the contract the parties avoid the application of tort law as a basis for liability. This makes it easier for the parties in the activity to calculate risks and avoid costly lawsuits. As regards insurance, by using the knock-for-knock principle the parties avoid the risk being covered under two insurances, i.e. the claimant’s property insurance and the wrongdoer’s liability insurance. However, for the allocation of liability to be effective the assured’s contracting party must obtain specific rights under the insurance, e.g. protection against subrogation. This is because the insurer has a right of subrogation against the wrongdoer upon payment of compensation to the assured for a casualty covered by the insurance. The wrongdoer still needs liability cover of the risk if the claimant’s property insurer may pursue a tort claim against such a party. This thesis is a comparative study of the rights of third parties under the hull insurance of drilling vessels effected on chapter 18 of the Norwegian Marine Insurance Plan 1996 (version 2010) and the London Standard Drilling Barge Form (All Risks). Moreover, it examines to what extent the insurance provisions arrange for a clear allocation of liability between the parties involved in the offshore drilling activity.