Targets: You and up to 5 adjacent friendly creatures.
As you cast this ritual, your humming and physical manipulation of the water creates a thin layer (౩ inches off of the body) of fortified and enhanced layer of seawater. The layer contains the exact temperature and pressure of the surrounding ocean. When diving to the crushing pressures, pitch black, and brutal cold of the depths, this layer acts as a layer of the area you cast the ritual in. However, normal physics apply outside of the layer. One must be in survivable ocean when the spell ends or face an unpleasant death.
I'm going to try to post some more aquatic spells/items once I figure them out. But this seemed like a tough aspect of real deep diving that was bugging me. "How am I going to get them down there?
I would contrast this to the level 4 Freedom of Movement spell:
One creature touched
10 minutes / level
Useful in many situations
No water breathing
Shell of the Shallows
Useful only in aquatic
Water breathing (sort of)
Typically, the 'Mass' version of a spell is 4 levels higher.
Persistent Spell extends duration of a spell to 24 hours, but is 6(!) levels higher.
Water Breathing is a 3rd level spell you pick up for free with this casting.
So the only thing that balances all this utility is how much less useful Shell is than Freedom-- Don't get immunity to paralysis, web, slow, grease, grapples, etc. etc.
What it does remind me of is a spell from a late 3.5 supplement:
AIRY WATER Transmutation [Air, Water] Level: Seafolk 6, sorcerer/wizard 5 Components: S, M Casting Time: 1 standard action Range: 0 ft. Area: 20-ft.-radius emanation centered on you Duration: 10 min./level (D) Saving Throw: None Spell Resistance: No
The other thing to consider is how the PCs might use the spell. At level 5, you are in a band where there are a lot of utility in spell choice. 5th level is available at 9th, but will a spellcaster really use up one of the spell slots for this?
I think I see it as a wondrous item effect, some sort of enchanted diving bell or a magic bottle of air-- the players would need to keep track of it and not lose it during the adventure, or an item with limited charges would keep the underwater expedition short and concise-- as you indicate, when the spell runs out bad things happen.
Hope this isn't too negative, I'm just reading this for balance.
Not negative at all man, I wholeheartedly appreciate the feedback. I probably should have put a bit of context with the the post. I'm running a (now) two person aquatic campaign. Wizard and ranger. Seeing as how there is only so much to do at shallow depths, I figured level 5 would be a decent time to get the story moving towards the kraken area. I have the storyline fleshed out in my post dungeonmasterblock.freeforums.net/thread/1792/kraken-fall
I know it seems pretty OP, but I thought, "they live full time in the water, it'd be used by pretty much everyone, so it'd be "common water magic" sort of thing. I'm also finding out I'm very good with ideas, terrible with mechanics. I like to be very loose when it comes rules, not that I don't care about them, just that I want to be VERY flexible. I live in a tiny Town in Maine, and the fact that I found someone to play besides my wife? They're lucky I'm not starting them of with wish spells I'm so jazzed.
Anyway, I'm definitely going to try to tweak it. I'm going to try to figure out how to try to adapt leomunds tiny hut so they have shelter down deep.
Really glad you built your group-- Any way you can get to play is worthwhile in my opinion.
If you're just going for flavor, it's pretty easy to make up a mechanic like you have-- in exchange for one 5th level spell slot, both players get to travel underwater and the adventure mechanics are easy-. I imagine them swimming like Mario who, you'll note, never actually needed to breath in the old games. Getting back to your game, you handicap the wizard player one of his valuable spell slots to serve a narrative purpose.
If you put the effect into a wondrous item, now you've added a mechanic with a dimension. Imagine a torch-- everyone needs to see, but only one player needs to hold the torch. You have set it up so only the wizard has one hand tied (or one 5th level slot in this case). If the effect is confined to a static item, like a torch of coral or some other poetic fantasy thing, then someone needs to maintain the device in hand, or in a worn item slot, or attunement, etc. It makes it such that the players have better agency over which takes the handicap.
In many cases, when party needs to have an aerial adventure the DM provides a magic carpet. It's a standard fantasy item to let the party adventure in a new environment, but it has certain limitations; someone needs to take action to direct its motion, and it's a static platform that the PCs cannot easily leave during an encounter. From a mechanical-narrative perspective, you are using a constraint on the players capabilities in the scene mechanically, and so creating some opportunity for narrative tension.
I think you would be well served to use the description of the spell i mentioned above-- I think it can be easily adapted to your narrative purpose and provides existing balanced mechanics--
This spell turns normal water (or watery solutions) into a frothy substance that is as breathable as air. Both air-breathing and water-breathing creatures within the area can breathe normally. Moving through airy water is easier than moving through normal water. Swimmers make a DC 10 Swim check once per round; they swim at their normal speed on a success, or half their normal speed on a failure. Creatures with a swim speed can simply use their swim speed without penalty. Creatures can instead use their land speed to move along the bottom at their normal speed. Creatures walking on the bottom do not pay any movement penalty for walking on sand, stone, or pebble seafloor and only pay 2 squares of movement per square of muck or mud entered (see Marine Dungeon Terrain on page 21). Finally, airy water negates underwater combat penalties for all melee attacks, although ranged attacks still take the normal underwater penalty. The spell does not filter or purify solid particles, so casting airy water on very turbid liquids, for example, would produce an area filled with dust or smoke (and impose similar penalties). Material Component: A small handful of alkaline salts.
I think putting the above effect into a bell or torch that has to be held by a diver adds an interesting dimension to encounters. Your PCs would need to remain within the sphere of effect or face ill effects of the deep ocean. It would be an issue if the object went missing or was knocked out of hand. There could be an interesting trade from one PC to the other to share breathing time while keeping good range. There's a lot you could do, and the above provides some mechanically sound and consistent rules to do it.
In this case, just adapt the effect that makes your scene run most easily and give it the constraint you find most interesting. So long as your are homebrewing the effects and rules of the spell, make it serve your narrative purpose as much as you can imagine. Currently, there is a dicey situation at the end of the day when the spell must be renewed. With this effect, you create a mini-crisis to continue adventuring, so use that tension to some good end.