The midwife said they will help support me to help me not tear, but that the flesh will be weaker there because I tore the first time. She said I shouldn't try to have a water birth because they can't support me as well under water,
I'm really surprised your midwife said that.

The flesh where you tore before has scar tissue, which is actually Stronger than regular skin, so you may tear next to it, but not in the same place.
I'm also really surprised that she said that they can't support you in the water... That's not true. I know a midwife who told me she was practically in the water with her patient one time because the laboring mom had a prolapsed cervix and she needed to support the cervix so it wouldn't come out as the mom pushed... (yikes).
Anyway, being in the water Helps Immensely because the water is Warm, which helps your perineal muscles & the skin stretch soooo much easier.
I had #8 at home, in the bathtub. He never did flex his neck so I had to birth the Full circumference of his head. I felt the "ring of fire" that I hadn't felt since baby #2! However, being in the warm water, I only got a skid mark with that kid.... vs my land birth with #2 where I had a tear (which I didn't even know I had until the doctor was stitching me up).
Another thing to remember is that your body has done all this before... Generally speaking, with baby #2 (or more), you are already "stretched out", so the baby comes much faster than the first one did, and the pushing stage is much faster as well.
It may help to have your midwife tell you when to Stop pushing (even if she's not actively supporting your perineum) when the baby's head crowns so that you can ease the baby out. That right there may well be the Biggest help to avoid a tear.
