I went to Rhodes yesterday with Yesil Dalyan. It cost 115YTL for the coach to Marmaris, and fast Sea Cat service to Rhodes. This gives about 6 hours for shopping, sightseeing etc.
Pick up was at 5.30am in Fethiye and we were dropped off at 9.30pm.
Apparently the Flying Poseidon hydrofoil that runs out of Fethiye is Kapoot ! Possibly won't be back in service this season.