The UK does not have a single maritime code. English maritime law is based in part on international conventions but also on legislation and the law of contract, tort, bailment, property and international law. But it is more than a collection of examples of general ideas - the sea is unique and needs a special legal regime.
Commercial shipping is an international business - certainty and international uniformity are important requirements. It often seems as though the content of a maritime rule is less important than the certainty and general application of that rule. It is also a business carried on in difficult or dangerous conditions, far away from the control or the people who will be responsible if anything goes wrong. The law needs to be adapted to this feature too.
Another characteristic of maritime trade is that activities are not carried on in commercial isolation. Contracts to carry goods, for example, are usually made in order to give effect to sales contracts. In practice, contracts to carry goods by sea are frequently of direct interest to third parties - buyers or lenders - and the law needs to take account of their interests as well as those of the original parties to the contract. All this means that maritime law is a chance to see how general ideas about law can be modified or adapted to make them work in a special context.