A few things have come up, so I gots questions for y'all.
1) Exploring a dungeon that we may make into our base of operations. There is a portal to the Plane of Water. Is the Plane of Water salt water or fresh water? It would be useful to have an uninterruptable source of water. If it is salt water, is there a spell or magic item to de-salinate the water?
Could it also be a source of food? Are there normal fish swimming in the Plane of Water that could be lured, fished, netted, or caught?
2) Encountered a few swarms of crabs underwater. Holy crap! Need area of effect, but the only AoE spells I have are fire and mind effecting. What do you think would be he best 1st or 2nd level Magus spells for such a situation?
3) Monkey fish gives you a swim speed of 10ft. If you have a swim speed, you can breath underwater. If you can breath underwater, you can cast spells without penalty underwater. Is all that correct?
Does the swim speed also give you a steady base to make piercing weapon attacks without the penalties for being underwater?
4) Tried the spell Blood Transcription on a creature that was using magic on us. However, turns out the creature isn't casting spells. It has an Ex (extraordinary ability) that is the same as the spell. Should Blood Transcription work? What if it was a spell like ability?
Mostly the Plane of Water is fresh as I understand it, but conditions vary across the plane and there'll be areas (volumes?) of salt water. Yes those should mix; no they don't. The natives do not include animals, and I expect eating elemental creatures will be unsatisfying to you.
Low level magus anti-swarm spells for underwater use. There's nothing good. Sonic scream does let you do something.
Yes it gives you a swim speed. No that doesn't let you breathe underwater - your chain breaks there (counterexample). You should be fine to stab things though per the table on this page.
I'm pretty sure blood transcription only picks up spells per its description.
Hmm... I will have to look for it. I was sure I remembered reading that if a spell gives you a swim speed, it gives you water breathing. Maybe I am mis-remembering.
Polymorphs do that, monkey fish isn't a polymorph tho'.
Dang! Yep, you are right, it is only a polymorph thing. I didn't remember it that way.
Ok, so if I use a polymorph spell that gives a swim speed, then the chain works. I can cast spells underwater without penalty. Correct?
Alter self into a merfolk and you can cast underwater just fine, yes. Except fire spells, you still have to make a check for those.