Krabi is an area of natural beauty, towering emerald green limestone karts and azure blue seas make the area stunning. What better way to see the area than from wave level ? There are several shops/companies that run sea kayaking trips, either with a group or self paddle. Like this one link but there are several on Ao Nang beach and you can negotiate yourself exactly what you want, from day trips to longer multi day trips.
An easy day trip is to circle Koh Poda and ‘chicken rock’, so named due to it’s likeness to a chicken. A local boat will transport you out to the starting point and you can then leisurely travel around islands, stopping at small secluded beaches when you will, enjoying a packed lunch and the natural beauty. You can even explore small sea caves and overhangs as you go.
Generally the trips are rather quiet and peaceful, as not that many people bother to go self power. You may see one or two ferries of, mainly Thai and Chinese tourists, but for the most part you can enjoy the feeling of being one with nature.
Certainly, I would rate sea kayaking in Krabi, Thailand as a five star activity and I cannot wait to be going there again!