You can also use octopus liqueur which is a consumable food item that gives the water breathing effect for the party member that drinks it.

Having nature magic is not mandatory but I do think you will have a rough time without it in at least one out of those two areas. That being said, it sounds like you are pretty far in so I would recommend trying to save those areas for when your party is strong and stock up on liqueur and crystal shards (which are purchasable from Gluckenspiel). Both areas have air pockets as well.

I would restart if I were you. Actually there are items that can be substituted, but not realistic given the number of times it is used.
If this is second lap and you remember the maps, perhaps it might be possible.
Likewise, arcane caster is almost a must for forcefield i guess. Forcefield trap's duration is short and it won't trigger If it doesn't hit the enemy.

引用自 sumaneko：

I would restart if I were you. Actually there are items that can be substituted, but not realistic given the number of times it is used.
If this is second lap and you remember the maps, perhaps it might be possible.
Likewise, arcane caster is almost a must for forcefield i guess. Forcefield trap's duration is short and it won't trigger If it doesn't hit the enemy.

There is staff for force-field.

Also recharge shards can be bought for gems and gems can be bought for banknotes. I finished game with 20 000 $. 1 gem costs 80 $.

I can confirm it's possible... but hard.

it's impossible to do a 100% secret without any nature caster. Some secrets need the spell to walk over water.

引用自 edlmdm：

it's impossible to do a 100% secret without any nature caster.

This is not true.

sorry there is an object for the spell i have in mind