Benagil Cave is where even non-kayakers go kayaking. It’s one of the symbols of the Algarve – a sandy beach inside a large cave, with two entrances and a skylight. It can’t be accessed from land, just by boat. Some of the big motorboats do a “hybrid tour” where the passengers are disgorged into double sit-on-tops for the last hundred metres. However, new regulations from August 2024 prohibit visitors from getting out onto the sand – photos like the one below are old news I am afraid. It is also prohibited to swim to the beach, but if you have brought your own kayak you don’t need to take a guided trip.
There are tour companies at Benagil Beach itself, although new regulations aimed at preventing overcrowding and accidents disallow rental (without guide) companies from operating in the area. You are still free to get a longer term rental from Decathlon or similar and carry it down from the car park. The tours don’t tend to run if the surf is greater than a metre high. The departure beach is small and south-facing so if southerly winds are strong (usually a winter phenomenon) then the surf gets up and you may be out of luck. Check the wave forecast ahead of time here. https://www.surfline.com/surf-report/praia-do-carvoeiro
The area is very busy in summer and you will probably come across many inexperienced kayakers falling over in the surf and getting in each other’s way, although this will improve with the new regulations . Launch from the beach and turn left keeping close to the cliffs. In high summer a lifeguard on a board maintains order, keeping everyone apart. If it is busy and there is no lifeguard, sometimes the motorboat drivers can get intimidatingly close – stay near to the left wall as you enter the cave and make sure you are seen.
If you want the place to yourself go either very early or late in the day, as many of the operators clock off before 6pm.
There are other (less popular but quieter), paddles on the surrounding coast, see Portimão to Albufeira coast. Further west is the other big kayaking attraction in the area, Lagos and Ponta da Piedade.