What about sailing? There are several websites, where captains are searching crew.
We just spend 5 weeks on a sailing vessel going from Tahiti - Moorea - Hiaunine - Taha - Bora Bora - Maupiti - Aitutaki - Tonga - Fiji.
We paid 37,50€ pp per day +10€ pp per day for food and fees (harbour, immigration, customs, etc) in a 8 person catamaran (we had a nice cabin for ourselves). Seeing these beautiful islands were definitely worth it! You just need a little extra money for activities (diving, whale swimming, scooter rental, etc.). We even had a paddle bord, diving equipment (incl. Compressor), snorkeling gear, etc on board.
We found the offer through www.handgegenkoje.de but there are also english websites, like e.g. www.findacrew.net
Better try sailing first though if it is for you...can be pretty rough (for the stomach) and you are expected to help out on the boat (cooking, cleaning, night watch, setting the sails, anchoring, etc), but it was a great experience!!!