Reece Myles-Meekums’ blistering 42nd minute goal secured a fourth successive league victory for the Hornets.
The former Worthing winger picked the ball up on the wing, before buccaneering towards goal and unleashing a thunderous effort past the Gulls’ goalkeeper.
The win also moved third-placed Horsham to within two points of the division’s summit, after both league leaders Dartford and second-placed Billericay Town dropped points.
Top-of-the-table Dartford left it late to rescue a 2-2 home draw with Kent rivals Folkestone Invicta, while Billericay – who are now winless at home in the league since February – slipped to a 2-0 home defeat to Cray Wanderers.
The Hornets travel to ninth-placed Carshalton Athletic this Saturday, before entertaining Cray on Good Friday (April 18).
Horsham then visit relegation-threatened Bognor Regis Town on Easter Monday (April 21).
See some of John Lines’ pictures from the game on this page and the ones linked, and read Horsham manager Dominic Di Paola’s thoughts in the West Sussex County Times, out every Thursday.

1. Horsham FC move to within one point of guaranteeing play-off place with Canvey win - the match in pictures
Horsham FC moved to within one point of guaranteeing an Isthmian Premier play-off place with a 1-0 home win over Canvey Island. Photo: John Lines

2. Horsham FC move to within one point of guaranteeing play-off place with Canvey win - the match in pictures
Horsham FC moved to within one point of guaranteeing an Isthmian Premier play-off place with a 1-0 home win over Canvey Island. Photo: John Lines

3. Horsham FC move to within one point of guaranteeing play-off place with Canvey win - the match in pictures
Horsham FC moved to within one point of guaranteeing an Isthmian Premier play-off place with a 1-0 home win over Canvey Island. Photo: John Lines

4. Horsham FC move to within one point of guaranteeing play-off place with Canvey win - the match in pictures
Horsham FC moved to within one point of guaranteeing an Isthmian Premier play-off place with a 1-0 home win over Canvey Island. Photo: John Lines