The incident started to unfold on Monday night (31 May).
The 52-year-old called police to report that the vessel was taking on water and he was unable to get ashore.
On Monday night and Tuesday, police, coastguard teams, a coastguard helicopter, and an RNLI lifeboat searched the sea and coastline around Newhaven Fort but were unable to locate him or the vessel.
Aleksander is from the Plumstead district of south-east London, where he has connections.
Anyone who has seen him or an inflatable vessel in the area or has any information about his whereabouts report online or ring 101 quoting serial 1404 of 30/05.
