We just finished playing Tides of Doom and had a great time. It was very difficult on the players and the NPC cleric ended up dying during the Sebastian fight. That fight could easily have been a TPK with only 2 characters standing at the end ( and they were very bloodied and only had standard actions left ). The other 2 characters were down with 1 and 2 failed death saves. I had to let the icon escape and not try to dominate anyone. They would not have made it through that.
In the anglerfish section, I got 1 PC in the water and attacked twice, then I had 2 more in the water once each. Other than the mesmerizing gaze, they went in by rolling a "1" on an athletics check while navigating the bridges. The drow rogue failed TWICE! It was hilarious seeing their faces when the "1"s came up and fish started chomping on them. The drow rogue also found both tripwires on the 2nd level. The hard way...
The garbage monster hurt them pretty bad too. After they got the red brigands warning, the got a little paranoid about it returning.
I didn't get too much into the extra info, except as background. I did have the Red Brigand arrow the message at them and also I poisoned them at dinner. One fun thing I did is to let them find out about Sebastian during one of the extended rests. They went to the fishing village section and found his abandoned house. He had built a crude altar in his bedroom and made some sort of bloody sacrifice. I went a little overboard with some of the extra descriptions and the PCs wanted to steal a boat and look for the "secret caves" that Sebastian had been overheard talking about. Not a boater among them!
The only problem I had was getting them to make enough corruption rolls. I got 2 characters with the minor effects, but nothing else.
They had a lot of fun though. Thanks for the adventure Ross!