My partner and I recently swam the outside harbour wall in Morro Jable (see map)
As you enter the harbour, before the Cafeteria El Muelle turn left on the car park, (there are usually a couple of lorries parked up) and follow the fence until there is a small opening between the cliffs and the start of the harbour wall.
It is rocky and so best if you have booties. My partner did, but I didn´t. Getting down isn´t too much of a problem, even in flipflops, but getting into and out of the water on the rocks is a little more difficult bare foot.
Its still a bit cold this time of year (April) but we have shortie wetsuits - which are a godsend - or I wouldn´t last very long in the water.
Visibility is great, much better than the other side of the marina/harbour....
We saw garden eels (first time in Canary Islands that we have seen them. I´ve read divers see them a lot, especially around Jandia, but not really snorkellers), the usual parrotfish, lovely green wrasse, bream (some quite big), damsel fish and small barracuda but the creme de la creme was the 2-3000 needlefish. (I was smiling so hard the water kept getting into my snorkel
Needlefish don´t like you chasing after them, but if you can get close enough and don´t thrash about or make too much arm movement, they don´t swim away as quickly, or at all. At one point I had a tornado of them all around me, and my partner the same (as in a second and just as plentiful tornado at the same time). There must have been 1500 per tornado at least, each one around the 12-15inches mark. Pretty special.
Unfortunatley no rays, sharks or turtles, but we will keep our eyes peeled and update as and when the sightings occur.