One of the other considerations you want to make is the amount of rope, known in the boat speak words as "rode" which I think comes from a Middle English term something like "at rode" which means "at anchorage" . This gets worse, because I think the word anchor comes from a Latin or Greek term to stop or stop a vessel by connecting it to the sea bed!!

I'll get my hat now!!
Anyway.....get as much "rode" as you can because the Danforth which Ed and I use will benefit from having the best "scope" (here we go again

) you can have. Chain at the Anchor helps with setting it and chaffing over rocks, but in a sportsboat a lot of chain is very heavy so about 6m would do. Oh and scope is the ratio of depth to length of rode to anchor.
In plain English, if you anchor in 10ft of water for an hour at slack tide dropping the anchor with about 30' of rode will suffice and to be fair this will hold most sports boats ok. With a heavy tide running however and maybe a little wind and water level rising to a possible 15' it would be worth having 30m of rope on board.
Hope this helps.
