That would depend upon the height and size of the fin and the thickness at the base.
PLA would be ok for small fins ( as long as they don't use fcs tabs) but for 9" singlefins it would be too weak.
Keep in mind that with 3d printing it isn't just a matter of the strength of the material but also of the bond strength between layers, which is typically weak with home printers. This can be overcome by printing the fin with the extrusion lines running vertically but that's not ideal for water flow.
It's all very well saying that doing it in PLA on a home printer can certainly be done right now, but you haven't proved that the result will be up to the job when riding waves.. We've spent the past six months proving that we can actually do it. There's a world of difference between our two positions. For example I know that ABS is not strong enough for the job on a 9 inch singlefin, because we have made ABS prototypes, and tested them to destruction in both static strength tests and in the water.
PLA lies between ABS and polycarbonate in strength, but I doubt that it would be successful for fins up to 9 inches or more when used in a home printer.
The key with bond strength is a heated chamber which most home printers do not have.
PLA is also extremely brittle, unlike polycarbonate.
Nylon is another interesting possibility and we have access to laser sintered nylon printing, but it's pretty risky and difficult to use for home printers partly because it creates highly toxic cyanide laden fumes when melted.
It's far easier and cheaper for anyone who wants to try one of our fin designs to just buy a fin from us.