Don't know the name of the boatman if it was even a company but I took a trip from the lovely town of Knightstown on Valentia Island. It's worth spending a day or two there. Be aware the crossing takes quite long and the seas can be quite rough. If you're prone to seasickness you'll still have to make the return journey. Have to say I found the trip worth it. Be careful on the stairs up to the beehive huts, the "stairway to heaven" as it's known. about 7 years ago
It's also important to determine which port you want to leave from; there are four. Where you leave from can affect your travel time. Check with the local tourism office for the most up-to-date info - http://www.ringofkerrytourism.com/.
Because of the limited access, the boat operators are quite consistent. Just make sure you're getting on a boat that stops on the island.
Two links to check out:
http://www.worldheritageireland.ie/skellig-michael/ about 7 years ago