Hi and welcome to the forum. I'm sure you will have a great time in Icmeler. As for things to see and do, there are so many - if you go to the main
Icmeler Online page (link above), there is an excursions section which will give you an idea of some of the trips on offer. These include things like jeep and quad safaris, horse riding and so on. I would say a "must do" is one of the lazy day boat trips, which let you see a bit of the area around Icmeler, but you can relax and sunbathe, swim and there is usually a stop off in Turunc or somewhere else. A Turkish bath is another must - preferably near to the start of your holiday to make the most of your tan! The Wednesday market is another idea - some love it, some hate it - but you've got to pay it a visit at least once, but don't forget to haggle!
I'm sure others will be able to come up with other suggestions for you.