Hi guys,
Guanabara Bay will be main venue for the boat races in the 2016 Rio Olympic games.
This beautyfull place has a problem - huge amount of waste.

I got idea to make a game which would turn peoples attention to it.
Concept of the game is to collect garbage from the water.
Player controls the little boat, rowing across the waters crowded by variuos types of the water transport, from the fisherman boats to the oil tankers.

I am making it with flambe 2D crossplatform game engine: http://getflambe.com/
Here is link to the simple mockup I made already:
http://gedi.biz.nf/garbay/

Any suggestions how to make game more engaging/fun and less propaganda?

You could start with something like the classic gold miner game idea for a bases, or something like a fishing game.

Thy are basic games but have a simple fun and addictive nature.

Make players collect trash and get score, scavenging games are fun.

Any suggestions how to make game more engaging/fun and less propaganda?

Hmm... One thought might be indirection, and "showing" rather than "telling": instead of telling the player "the lake is heavily polluted, this is terrible and you must fix it!", instead put the player in a position in which the untoward effects of pollution are clearly visible, and from which they can do something about it.

Without doing research on the pollution in question, I'm not sure of what specifics to suggest, however. To give an example using a different sort of pollution, air pollution might be addressed by placing the player in charge of a region over a significant period of (accelerated) time--thus (hopefully) providing a perspective from which the effects of such pollution are clearly visible in the environment. In such a game I might also suggest that eliminating pollution not be the central goal, but rather something that arises in trying to reach the central goal--if the player is required to manage animals, for example, the pollution might be one of the hazards to the player's charges.

Your demo looks very nice. To make the game more fun and engaging, you could try using the Pac-Man method. In that game, the player has to eat all the pellets to clear each level.

So in your game, the player could pick up all the trash to clear each level. The challenge might come from avoiding collisions with those larger boats or beating a time limit.

If you'd like to, you could add a score system to the game, awarding points for all the trash collected and a good time (like the older Sonic game had done with rings and your remaining level time).

I hope I was able to help. Good luck with your game!

- Rye

Simulating a bit of current and fluid dynamics might be interesting. Not necessarily a realistic simulation, but something to make your heading a bit unpredictable when you're in the wake of the big boats. You can do this with a cellular automaton... and even cheat a bit and only iterate over visible cells.

For a bit of progression, you could reward the player for the trash picked up and let them buy better boats (bigger, faster, less perturbed by wake & currents, etc.), implements to (say) pick up trash a little further away, minions in little boats that circle your boat, picking up trash you've missed... anything where the player can feel that they're becoming increasingly efficient and powerful.

I don't think it's preachy or propaganda-y. My advice would be just to stay solution-focused ("Let's do something about this, so that we can show off our beautiful coast"), rather than problem-focused ("How awful people are for destroying our coast, and how awful everyone is for not caring").