In connection with my quest to discover where my ancestor Malcolm Kerr (1822-1898) might have been laid to rest I contacted the National Maritime Museum in Greenwich to see what is known regarding the rules & regulations for burials at sea pertaining at the time.
The Births and Deaths Act, 1836 (which set up the system of civil registration in England and Wales), the Registration of Births and Deaths Act, 1874 and the Merchant Shipping Act, 1894 gave instructions to Captains on how to register the actual death, but contained absolutely nothing dealing with the circumstances, such as the minimum depth of water or distance from the shore, under which such a burial could be undertaken.
My initial astonishment at the lack of any such legislation existing at that time has been tempered somewhat by the reflection that many souls were lost overboard (or in wrecks) close to land and yet their bodies were never given-up by the sea.
With that knowledge and experience perhaps it was felt unnecessary to specify a depth of water or a distance from the shore? It would appear to have been a matter of discretion as to whether to perform a burial at sea or to take the body ashore for burial, just so long as the actual death aboard the vessel was correctly recorded.
It also means that, whilst not proven, Malcolm could indeed have been buried at the spot where he died in the Horseshoe Bay of the Sound of Kerrera...
Note: I am extremely grateful to the Information Assistant at the Museum's Library for his diligent research into this topic.