Go to "Find my Past"
Go to Deaths and Burials
Go to British Overseas 1761-1994
Go to GRO Marine Death Indices 1903-1965
You may be lucky and find him there. As already pointed out Kew holds comprehensive records for DAS 1929 in BT334/88 and BT334/89 both for overseas and British waters
If you find nothing in GRO Marine Death Indices 1903- 1965 just send me a PM
If he died at sea and the body was brought ashore then his death would be recorded in the usual way.