Here’s a quickie dungeon for you, featuring mer-mongrels (essentially aquatic orcs), just in case you need something dark, wet and dangerous for your game.
This is underground and near the sea. Sea water flows down the entrance corridor. Everything is slimy and the water is about 2 feet deep (so gnomes and halflings might need floaties) throughout.
There are clumps of phosphorescent sea weed here and there, giving a dim glow to the caverns – so dim as to be useless, but enough to create weird, wavering patterns on walls.
HD 1, AC 13, ATK Claws (1d4) or weapon (1d6) or barbed net (1d3 + entangled), MV 20′ (Swim 40′)
1. Corridor is broken here by a waterfall – water leaking in from the ceiling. Just on the other side of the waterfall there is an aquatic assassin vine attached to the ceiling. Just beneath the waterfall, to the extreme left of the corridor, is a pit that leads to the corridor just to the right of  on the map (the one that leads to area ). That corridor is completely submerged until area .
2. Two lacedons are chained to the walls here. The mer-mongrels have a winch in  that shortens the chains, but otherwise the lacedons can wander throughout the room.
3. Water swirls around the walls, ceiling and floor of this tunnel, creating a vortex of confusion. Save vs. confusion or become dizzy (-1 to hit, AC and save) for 1 hour.
4. Three mer-mongrel guards are in this room playing a gambling game that involves plunging half a coconut into the water and seeing which player gets splashed. Each has a shagreen pouch holding 1d10 gp. One mer-mongrel has a barbed net, the other two have tridents. All three have daggers.
5. A small natural chimney in this room leads to the surface. The air is fresher here.
6. This is a supply room, containing bits of flesh wrapped in seaweed and stuffed into cubby holes, floating bottles of wine, floating boxes of candles and an odd assortment of tridents and daggers (1d6 of each).
7. Two mer-mongrel acolytes dwell in this room. They have silvery bodies, and each can cast one 1st level anti-cleric spell (chosen by GM). They are armed with footman’s maces with heads shaped like octopi with opal eyes (worth 35 gp each). A curtain of barbed chains blocks the passage to .
8. The high priest of the mer-mongrels (3 HD) dwells here. He can cast two 1st level anti-cleric spells and one 2nd level anti-cleric spell, and wields a mace like his acolytes (but with pearl eyes, worth 150 gp). The room is also occupied by three white fish who roam around randomly, but who can be commanded by the high priest to swim in a circle, creating either a magic scrying pool or a magic whirlpool (per a water elemental). A sunken iron chest holds 250 sp, 50 gp, a gold bracer (65 gp) and a potion of healing in an old rum bottle.
9. Mongo, the living clam god (a giant clam) dwells in this chamber, the temple of the mer-mongrels. The clam rests in the alcove in the far portion of the cave, and a coral altar has been set before the clam. A young man in rough shape is chained to the altar as a sacrifice. The altar juts about 1 foot above the water, and there are many candle stumps and a few burning candles on the altar. Right before the altar there is a submerged pit (save vs. falling – no damage from fall, but 5% chance of drowning do to an accidental inhalation of water).
10/11/13. Each of these chambers is inhabited by 1d6 mer-mongrel males armed with daggers and blowpipes from which they shoot poisoned sea urchin darts (save vs. poison or slowed for 3 rounds). Each chamber has a small stone chest containing 1d4 x 50 sp and 1d6 x 100 cp. One of the mer-mongrels has a small topaz (30 gp) hidden under his loin cloth.
12. Several sea urchins are kept in this alcove. The water here is envenomed by their presence (save vs. poison or 1d6 damage).
14. This spawning chamber is home to five female mer-mongrels. They are armed as the males, but also carry two nets. There are three young in the room, and they will fight to the death to defend them (and send them fleeing into  at the first sight of trouble. A stone chest here holds 200 gp and three bottles of fine wine. The chest is trapped with a sea urchin spine (save vs. poison or 1d6 damage).
15. I forgot to put this number on the map!
16. This is the lair of Yort, the chief of the mer-mongrels. He is a erudite man (he trained in the humanities at a sea elf university) who returned to his tribe when his father was slain by adventurers. Yort carries a +1 trident that can make the water boil in a straight line up to 20 feet long (1d10 fire damage, save for half damage) three times per day. He also has a silver dagger and a chest containing 500 gp, 1,200 sp, a small sapphire (200 gp) and a bottle of giant octopus ink. Yort will offer to pay adventurers off if they leave he and his people alone, but if a child is harmed will pursue them to the ends of the earth to exact bloody revenge.