The Shark Quest: You can sell tigersharks to Gortani in the Rip for 150 gold apiece.. Gortani is in the north west side of the palace. Careful, the sharks stun.

Letter Quest: Take the letter from Fyanthis, get the rose from the road to the temple above Riparium and take them to Takleia, the Queen. This gives experience, I guess, since there's no gold reward.

Kraken Quest: Get the astrolabe from near the entrance to the whole underwater area and the compass from Neraoes' temple and give them to Nishir who needs them to summon the kraken. He will then instruct you to say the word "Shalavante" to complete the ritual. The kraken will appear in the upper part of Riparium, not in the city, so you should be immediately safe. But, you might run across it leaving the area, and of course it might kill others. So it's polite to do the second part of the quest to banish it again. Plus you get 2k gold for doing it. 

Go and visit the king in the castle and say "kraken" to him. He'll give you a key. Go a few rooms south of the king, unlock the chest and get out the crystals. Now you must GIVE CRYSTAL to each of the polyps in the area. One of them is in the "farms" area east of the castle. One of them is on the upward path between the city and the upper ocean area. And yes, you'll have to go back up there to complete the quest, and yes, the kraken might eat you. Be careful. There are a couple more polyps up there. Once you run out of crystals, go back to the king and he will banish the kraken, and give you 2k gold plus some experience. Huzzah!