The reef to the right hand side of the harbour is considered one of the best breaks in the UK and has been the proving ground for many of the current generation of British pros
The wave is not a beginners wave at all - breaking with extreme power on to a shallow, uneven, barnacle encrusted reef, the potential for mishaps is great! Many a time have I played pinball with the rocks here whilst caught inside!
The wave itself is a fairly short left and right of varying quality depending on the swell direction and state of tide. The right is more popular possibly owing to the fact it breaks into an extremely deep channel (the harbour mouth). The right often provides at least one barrel section.
The left is slightly faster and more walley. It also often provides a decent barrel but the risk for taking a beating is a bit greater with the channel not being quite so defined
There is also a wave that breaks in front of the pier. It's got a short ugly left off it and a slightly longer, slightly dodgier right. It only seems to get surfed by bodyboarders which might give you a clue about how gnarly it is!
The ideal conditions are low-mid tide (low for the left), with a south-westerly swell and a north-easterly wind. However, the wave is so much superior to most beach breaks it's often worth a look.
The bad news about Porthleven is the crowd. When it's good all the top surfers in Cornwall are out there, plus the locals. Unless you're prepared to charge and dodge fibreglass then this probably isn't the spot for you! You have to put in a bit of time here and not be afraid to get any waves.