Aquatic conveyance right behind (4)
I believe the answer is:
raft
'aquatic conveyance' is the definition.
(a raft is a basic boat)
'right behind' is the wordplay.
'right' becomes 'r' (common abbreviation).
'behind' becomes 'aft' (aft means towards or at the end of a ship).
'r'+'aft'='RAFT'
(Other definitions for raft that I've seen before include "large collection" , "Floating platform of logs, planks, etc" , "Flat, floating platform" , "Simple craft" , "Makeshift boat" .)