Topic: Suggestions for underwater adventure?

[Arioch]

So tomorrow I'm going to run an adventure which include the exploration of a partially sunken temple. I'll leave to the PCs the task to find a way to survive underwater for the time required by the exploration, but I would like to throw in some additional water-related hazard, just to make things more difficult/interesting.

What I do not want are combat encounters, the adventure already has plenty of chances for combat (even challenging ones) and the party is composed by only 2 PCs...

Do you have any suggestion? How can I make my underwater temple more interesting?
Thanks!

[ToM]

Oh I'm sure there's a lot of nasty underwater critters out there, and you can make the whole thing more difficult by limiting their movement and capabilities somewhat.

BTW, are your characters able to provide movement/breathing underwater through magical means, or must they swim and hold breath?
Some time ago, I made a party of PC went through an underwater trail to approach a distant island in the Sea of Rhun in Middle Earth to avoid pirates and other hazards. I thrown them into a side quest to find magical pearl from a giant oyster that lived out there, which will gave them, if held in mouth, the ability to breath underwater. It was funny because it both added some "setting specific" flavour and limited their options, because if fighters can still able to fight, magic users might be seriously hampered (apart from mentalists).

Also, as obvious, I threw some sea monsters at them (giant eels, and a turtle dragon).
Very funny indeed.

[rdanhenry]

How about a thieving crab?

Schools of fish and patches of seaweed can provide reduced visibility.

Water will have moved things about and caused a fair amount of destruction. Searching through sand for lost treasures could turn up all sorts of things. Important markings on walls or objects can be obscured and partly lost.

Maybe there was a stone basin with a Symbol to create holy water when it was filled and it has been going off once a day since it sunk. What effects would a high concentration of holy water have?

A library that is in the submerged part, but is sealed. They need to recover as much as they can of the valuable books, scrolls, maps, and the like, but they need to do it without unsealing the room and flooding it.

Don't forget to describe a lot of the fauna, including "threatening" fauna like sharks, for atmosphere. It doesn't need to be a combat encounter to be noticeable. Have a few "objects" that move when not expected.

[jolt]

If the underwater portions are directly connected to the ocean/river whatever, currents can change very dramatically as you move up and down in the water and can be very strong.  Magical effects could also cause events like whirlpools and water spouts even in areas where they might not otherwise appear.  Brackish water could have all sorts of germs and diseases in it.

jolt

[Ido Tamir]

Maybe an underwater lava flow or volcano..
Think about huge dark pillars spitting molten rock, making the waters around them dangerously hot...

[GrumpyOldFart]

Even simple, basic stuff. Getting your foot caught in a crack between 2 rocks is completely different if the first thing you do is check how much time is left on your waterlungs spell.

If you've taken even 1 hit of blood loss, every predator within a mile or two downstream of you knows exactly what the state of your health is.

[Arioch]

Thanks guys, great ideas!
I'm probably gonna use almost all of them 

[markc]

 Reading the above I came up with these;
 1) How are they able to see under water? How far can they see?
 2) How do they navigate? What obstacles are in there path?
 3) How long can they be under-water? Think ticking clock?
 4) Currents can be very powerful and can force people into areas they do not want to be. Maybe this is one "trap" to avoid?
 5) Underwater terrain can be just like above water terrain so do not forget mountains, valleys and planes.

 Maybe have a number of underwater air holes or air dwellings that the PC's have to arrive at by a specific time. This would play into using multiple potions of water breathing and having to travel long distances.

MDC

[Arioch]

1) One of the party memebers is a seer so no problem for this (at least for her)
2) They'll have to swim around in underwater tunnels, surely not an easy task! 
3) This will depend by the solution they'll find... if they can't find a good long lasting solution I'll probably let them find some air bubbles as you suggest!
4) I've put a "trap" mad solely by a metal grate, currents will smash them against it if they can't find a way to avoid that!

Thanks again for the suggestions!

[dutch206]

Unless your characters have the ability to breathe underwater (naturally, magically, or herbally), I would impose a strict two minute time limit on being underwater.  I think that's about the longest a person can hold their breath without drowning.  Also, don't forget hypothermia rules for water under 50 degrees (F).  I think the environment should be more frightening than whatever the monsters are.

[yammahoper]

another good trap in underwater structures is the "hollow room".  Put something interesting on the wall so the PC's will take a look, like a shiny sword that gives off a faint light.  The glow alone will draw them in, then when they touch the sword, WHOOF, the wall collapses dragging them into the room.  A monster can be in the room, but the sudden bashing around, loss of orientation with falling rocks/cave in that seals the room FOLLOWED by being in pitch black muddy water were light is almost useless...oh yeah, its a goody.

Remember, invisible monsters recieve a +100 DB and can easily gain flank/back/surprise mods (that's a +55 fyi).  With that kind of DB and OB bonus, if you do use a monster trap, you can use some creatures that normally would never slow or bother the PC's, like biting eels that score an A electric crit with any bite crit, pirahna, or any biting fish with a 30-50 OB (instead of the massive 120 OB or so sharks).  Just remember to roll one attack against a PC for the group of fish, not one attack per fish, or ya might as well just rip up the character sheets.

[dutch206]

Remember, invisible monsters recieve a +100 DB and can easily gain flank/back/surprise mods (that's a +55 fyi).  With that kind of DB and OB bonus, if you do use a monster trap, you can use some creatures that normally would never slow or bother the PC's, like biting eels that score an A electric crit with any bite crit, pirahna, or any biting fish with a 30-50 OB (instead of the massive 120 OB or so sharks).  Just remember to roll one attack against a PC for the group of fish, not one attack per fish, or ya might as well just rip up the character sheets.

Not sure what you mean here.  If you mean "Invisible" as in the spell, I am pretty sure that the water would outline their position.  If you mean "Invisible" as in "Who turned out the lights?", remember some races have darkvision.

[jdale]

I wouldn't allow creatures with Darkvision to see if the reason for the lack of visibility is so much sediment mixed up in the water that there is no visibility. It's like seeing through thick smoke.

As for the separate issue of creatures who are Invisible in the sense of the spell, that is a judgment call. If you assume that the spell replaces the image of the invisible being with a space that has the same refractive index as air, then it will look like a person-shaped air bubble. But I think that's injecting too much science at the expense of magic. There's no reason why the spell couldn't match refractive index with water. I would say the space is more transparent than water, but you would have a hard time spotting such a thing, if you are looking at it through water and with more water behind it. The "fringe effect", which blurs the outline of an invisible person, will actually work in favor of the invisible person here, preventing a sharp outline. It would be easier to see the invisible person if the water was particularly cloudy, just like an invisible person standing in smoke.

[RandalThor]

One of the biggest hazards underwater is getting trapped. So something that could collapse and trap them forcing them to find a way out could be interesting.

[Arioch]

Thanks guys, I run the adventure the other day, the PCs had a little trouble figuring out how to breath underwater, but in the end one of them (a seer with good lachemy/herbalist skills) managed to prepare a "waterlungs" potion.
They still had to deal with currents, whirpools, dark water, etc... 

I also made them "encounter" a bed of a strange, glowing seaweed which attracted and trapped fishes like an underwater carnivorous plant. They discovered that it was harmless for humans, as it was able to trap only small fishes, but at first they got quite scared, fearing of being trapped and running out of time...

This thread spawns great ideas, keep posting! 

[markc]

I also made them "encounter" a bed of a strange, glowing seaweed which attracted and trapped fishes like an underwater carnivorous plant. They discovered that it was harmless for humans, as it was able to trap only small fishes, but at first they got quite scared, fearing of being trapped and running out of time...

 Also it leaves open a good reason to go back. It is also wise of the GM to try and use the same prep material as many times as they can. That is if it still makes sense and the players buy the reason to keep going back.
MDC

[mocking bird]

Step 1 - Don't tell the players it will be an underwater adventure as a 1st level character needs just as much air as a 100th.

And think undead - they don't need to see or breathe.  Skeletons make great underwater scavengers or barge pullers.