Best way to allow a warrior to use their slashing weapons underwater

Our party needs to go underwater. Our party also includes a warrior who is heavily specialized into a pair of +1 keen gold great scimitars, which deal slashing damage and thus take substantial penalties underwater. Because of their specialization, switching to another weapon also amounts to a substantial penalty. So either option is going to make the character have limited ability to contribute, and likely make the player not enjoy the session. We’re trying to brainstorm the best way to prevent that.

We do not have an opportunity to select new feats, or take levels in other classes, before we need to do this. We are 10th level, but most of us do not have anything to particularly contribute (a 10th-level crusader, a 10th-level beguiler, a multiclass character with the manifesting of a 6th-level egoist but powers tailored to self-buffs and battlefield control).

We do have a character with the spellcasting of a 9th-level wizard and something of a specialty in scrolls. They’re specializing in familiars, with Improved Familiar and four levels in the spell sovereign prestige class, and the changeling wizard racial substitution level from Races of Eberron, which allows their familiar to switch to any other kind of familiar as a full-round action, including into a living spell of 1st or 2nd level, so we potentially have access to a lot of spell and spell-like abilities that way.

We also have numerous NPC allies who could provide access to other spells that might be scribed with the wizard’s assistance, or even added to the wizard’s spellbook. There might plausibly be magic items we could borrow (we have a lich, a dragon, and a fey queen among our allies), and there’s an NPC artificer who might be able to create something in the time we have allotted (maybe three days), if it’s cheap enough.

Note that changing these weapons to another type—which we considered—doesn’t work because heavy-metal weapons require Exotic Weapon Proficiency in precisely the type of weapon, so the warrior wouldn’t be proficient with, say, +1 keen gold rapiers. Changing the +1 keen gold great scimitars to deal piercing damage—without making them anything other than great scimitars—might work, as would anything that says you can use non-piercing weapons underwater without penalty.

Freedom of movement, a 4th-level spell for most classes, does the latter explicitly. It has a range of touch, and lasts 10 minutes/level, so it’s plausible that the wizard could cast this on the warrior, but we don’t know how long we’ll be under. For all we know, the entire dungeon may be underwater the entire time. We have water breathing, so the wizard could re-cast freedom of movement, but that is dedicating a lot of the wizard’s second-highest-level spell slots, plus it’s possible for the wizard and warrior to get separated.

Heart of water is a 3rd-level spell for a few classes—including wizard—that can be expended to get a 1 round/level freedom of movement effect, but it’s self-only.

But the key thing to me is, the ability to use weapons underwater is a tiny fraction of freedom of movement’s power. Is there any spell that does just that? Ideally for a longer duration, and at a lower spell level? Any cheap magic item?

• @KRyan Well, then, he should upgrade. :-) Yeah, don't blame the crystal. It's kind of awesome. And at least magic vestment is only a 3rd-level spell. Can your buddies get up to caster level 12? Then scribe the scroll extended? It might be worth it, especially considering alternatives like airy water or cloak of the sea. Oct 31, 2021 at 16:36