select form from mytable where form ~ '^Canal$|^Drain$|^Foreshore$|^inlandRiver$|^Lake$|^lockOrFlightOfLocks$|^Marsh$|^Researvoir$|^Sea$|^tidalRiver$|^Transfer$'
You do not need to repeat the boundary metacharacters on each branch. You can assert their presence just once and then use parentheses to group the alternations.
