Warranties in marine insurance policies can take varying forms, from a common survey warranty to a unique provision inserted at the whim of a particular underwriter. Depending on the type of provision and the law applicable to the interpretation of the clause, the breach of a warranty may void or suspend a policy altogether. Alternatively, in certain jurisdictions or in certain cases, the breach may void the policy only if the breach is causally related to the loss or the breach increases the risk. In other situations, the provision may be unenforceable under state statute or under state law rules of contractual interpretation. This Article provides an overview of the treatment of a breach of warranty by various courts, beginning with an overview of various courts’ treatment of particular clauses and concluding with a discussion of a recent case example regarding a breach of an express seaworthiness warranty in a protection and indemnity policy.