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.
The Sea Rose Quest
Deadly wounded from a fight with King Nissandar, Fyanthis, the secret lover of Queen Takliea asks for a last favour. Take a letter for the queen from him, then look for a sea blue rose somewhere northeast of Delos. Return to Riparium and deliver both rose and letter to Queen Takliea.
You have to find the Astrolabe and Compass and bring them to Nishir. He will then instruct you to say the word "Shalavante" to complete the ritual. Do so. 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!
The Trident Quest
Talk to Xahlen, the city guard in Riparium and he will give you a key to a chest in the storage room. Take his trident from there and hand it over to him. You will be rewared with 100 gold sovereigns.
The Guards Quest
For each killed Riparium guard loyal to Prince Nishir you will be rewarded by King Nissandar with 500 gold sovereigns.
The Circlet Quest
Slay the ghost hidden in a sunken ship in Riparium and take the key it drops. Return to the surface and search for a chest located somewhere northeast of Delos. Get a beautiful circlet from the chest and bring it to King Nissandar, who will give you 550 gold sovereigns for it.