Ideas for Aquatic Encounters?

[Palanan]

I could use suggestions for interesting aquatic encounters—anything more inventive than “you’re on a boat and you get attacked.”

The party has just hit third level, with several tagalong NPCs, and I’d like to give them a memorable journey down a fast, cold river. What could I challenge them with?

[ColorBlindNinja]

If it's monsters you're looking for, you might want to take a look at Stormwrack, if you have that book.

EDIT: This might help: Aquatic Monsters

[AnimeTheCat]

I could use suggestions for interesting aquatic encounters—anything more inventive than “you’re on a boat and you get attacked.”

The party has just hit third level, with several tagalong NPCs, and I’d like to give them a memorable journey down a fast, cold river. What could I challenge them with?

Have them see a storm ahead. If they're captaining the ship have them roll Profession (Sailor) to see what they can determine about weathering it. If the roll high, they think they can safely navigate it and your encounter can take place in the storm. If they roll low they go around and encounter dense fog (as the obscuring mist spell, but everywhere) and the encounter takes place in there. Either way, you have a ship that is ringing it's bell for help. When the party boards, they find it to be a ghost ship. There's something off though, the soup pot on the fire looks like it has just been tended to. The beds are still warm as if just laid in.

IT'S A TRAP! Suddenly, when the party is on edge, pirates reach out of hidden compartments in the floor, walls, and ceilings and jump out of barrels in a surprise attack. The rest of the encounter is navigating back to their ship, fighting off the smuggler pirate crew.

EDIT: After escaping, you could have the pirates give chase. With fog or a storm to contend with the party's ship would probably be given a run for it's money, so have someone (an NPC or PC) spot an inlet that the party can make their way to to evade the larger pirate ship. As they do this they run aground possibly throwing some NPCs and maybe a PC overboard.

[ColorBlindNinja]

You're walking by the river, when suddenly, a gigantic crab scuttles out of the water's depths!

(Don't actually do that unless you want a TPK.)

EDIT: Second monster in that link.

[daremetoidareyo]

If they are going fast paced downstream, some thri-kreen jumping with dual spears from the riverbanks to subdue the boat and take it's goods would make a great battle. After four rounds, the boat goes further downstream and the beta squad of thrikreen clerics and psions with readied actions join in.

[Telonius]

Reward for getting to the destination quickly, but tempting/necessary delays.

Man overboard! Rescue the person before the crocodiles/anacondas/shrieking eels get him.

Environmental hazard: rapids. Steer the boat past rocks; failure makes it damaged or slower.

Lorelai; siren lures you to a dangerous situation.

Witness a crime; people on the shore getting robbed by a bandit. Do you stop to help?

[ColorBlindNinja]

Lorelai; siren lures you to a dangerous situation.

Are these monsters from a 3.5 book?

[hamishspence]

Sirines are from 3.0 (updated to 3.5) MM2 and fill a similar niche. There's a Siren PRC in Savage Species, as well.

[Uncle Pine]

You're walking along the river (or paddling through it), when you hear laughters and ale-tuned belches coming from upstream. They get closer and closer until a squad of 8 bandit dwarves harmed with harpoons appears, riding barrels down the river. There are more barrels than dwarves and a rowdy song seems to come out of one of the empty ones (inside of which a drunk dragonfire inspiration halfling bard is hiding). The dwarves' harpoons start crackling with lightning. Roll initiative.

[MeimuHakurei]

Aboleths are always a joy to DM for in a fight - Underwater, Grappling and Psychic Combat rules, oh my!

[Nifft]

I could use suggestions for interesting aquatic encounters—anything more inventive than “you’re on a boat and you get attacked.”

The party has just hit third level, with several tagalong NPCs, and I’d like to give them a memorable journey down a fast, cold river. What could I challenge them with?

Things on the boat go wrong.
- Fire.
- Theft.
- Stowaway.

The river isn't behaving as expected.
- There was rain recently, so there's flooding, and the river is moving faster than usual. A log jam needs to be removed before the boat can proceed.
- Spring is here, so snow is melting, and that means avalanches. Fallen boulders and ice have created unexpected shallows, and the boat has run aground. Boat repairs will take X days (fewer with PC creativity), or PCs can forage / explore the area.
- There's been a drought so the river is attracting some unusual creatures. The PCs spot one which would be valuable to hunt.

Monsters attack, except interesting.
- Drunk pixies and nixies have a betting pool (literally a pool of water with gold & pearls in it) and compete in stealing the best item from passing ships. They're looking for something unusual and dazzling, not necessarily the most valuable thing.
- Some kind of river monster is eating the rats in the hold. The problem is that it's doing this from outside the lower hull, its rat-hunting tongue making holes which need to be patched. Run it as more of a puzzle than a combat.
- Lizardman thugs are collecting a toll for passage. They look very cold, and they very much do not want to be here doing this.

[AnimeTheCat]

I may have misunderstood the basics of the situation... I thought about an open-ocean encounter. For a river encounter I would say;

As the party is making their way down (or up) stream, they encounter a problem. The river has been impeded by fallen trees (known to the DM to have been orchestrated by Troglodytes!). The party (and NPCs) must decide how they want to proceed, aka clear the blockage or go around (pull the ship out of the river and drag it around). As they are proceeding around the blockage, troglodytes attack from the surrounding land (can be either rocky or wooded or tall grass or a combination of all of them. Just make sure the blockade matches the environment, i.e. if wooded: trees, if Rocky: boulders). They start with a volly of javelins before closing in and trying to throw people in the river for the river monsters to devour.

If the Troglodytes start losing, they retreat. If the party pursues, they continue to encounter the Troglodytes, only they are fighting more ferociously than ever. Eventually the party will discover that the reason the Troglodytes attacked in the first place was because their lair was located close by. This can be an entire mini-adventure that takes place on or around a rocky wetland, which would lend itself well to a Troglodyte lair. Multiple stream/river crossings. You can also use cold weather and hypothermia to your advantage as well, should you so choose.

[daremetoidareyo]

Being harried by Flyers while on the water is always really fun. An anthropomorphic bat raiding party. Maybe one of the NPC's has some history with these flyers. I would deck them out as Druids with imbued summoning, and have them cast summon Nature's Ally with imbued summoning the Auto buff them with jaws of the Moray. Nothing is worse than eagles flapping in your face while they month's down on your collar bone.