Looking forward along the gun deck.
en.wikipedia.org/wiki/18-pounder_long_gun

Given their weight - 2.4 tons [2425Kg], it is probably just as well those long guns are replica (glass-fibre) 18-pounder "Blomefield Pattern" cannon.
They would require a team of men to operate - typically six to haul it about, one or two to swab & load, one [the gun-captain] to aim & fire, and a powder monkey, it could be done with six or even as few as four.
Properly trained, good gun crews could fire three rounds in five minutes. Later in an action, the discipline of broadsides might be discarded in favour of fire when ready.

If she had ever been fully gunned, Unicorn would have had 28 of these on the gundeck
{and 14 32-pounder carronades [smashers] - plus 2 9-pounders [chasers] and 2 more 32-pounder carronades on the forecastle}