To answer SunnyC's original question.... there are trips from the small harbour in Plakias several times a day every day when I've been in August. These go out to nearby beaches, such as Rodakino and Preveli. The ferry to Gavdos runs from the big harbour but you would need to stay for two to three nights in Gavdos. All trips depend on the weather - the wind can mean that people are stranded for several days in Gavdos.
So far we haven't done any of the trips, but are thinking of going to Gavdos next time. The ferry hardly ran last time we were there due to high winds.
There are also bus and walking trips available, including one to Balos which includes a boat trip. These can be booked through any of the travel agents (as can Gavdos), or through the Olympic rep if you are on a package.
Someone mentioned the bakery in answer to one of your other threads, and I agree the big one is marvellous. However - there is also one at the end of your street from Dora, which has nice bread and cakes and the Argo cafe also had good cakes to take away. That will save you a bit of a walk.
Enjoy your holiday - you seem very keen to find out everything before you go, so you don't miss anything, and this is just the place to find out.
I wonder if Shinaria meant squid - because I've certainly never seen grilled penguin on the menu anywhere!
Arnaki