What to wear under a tail that won't ride up?

[Trade Winds]

I will be swimming in my FinFun tail for the first time in a couple days, and discovered upon experiementing with my three bikini bottoms (no Spongebob pun intended) that they each ride up on the rear, and show above the waistline of the tail (which has been pulled up to my belly button). Even tho it is barely noticable and I do nothing "professional", I hate breaking character or ruining my costume by having skin ot clothes showing. Solving this is essential!!!

My question...should I make my own bottoms for my tail? Even the skimpiest and lowest riding of my bottoms showed above the waistline, so I am thinking hunting for a new swimming suit won't help. I could just get a matching top/bottom set from Fin Fun too. Advice?

[Mermaid Galene]

I wear a net belt, or even better, a nice scarf as a belt to cover the waistline of my tail. Works great; you can adjust the scarf to cover what needs covering.

[Mermaid Miel]

I have worn Tankini's, Swim-skirts, Swim-dresses and even Normal dresses (cheap fancy ones that I don't mind ruining.)
I also find that a thick pair of skin colour tights under light fabric tails, or dark tights under darker tails can help hold the fabric in place and hide any fading in the fabric... unless the tights have a pattern, then it only highlights it!

[Meshy]

I like the FinFun swimsuits. They're awesome on coverage and (I have a big butt and I cannot lie!) they fit great. I went up a size though. I fit into their Women's Small tail size, but got a Meduim bottom. I'm glad I did! The even better part is you can match them. (or not! I have matching bottoms and one has a different color top) If the fin does happen to fall at the waist, you still have your bottoms to save you from total embarrassment. It's also fun when I have to leave the pool and kids see that my swimsuit matches my tail! I must be a real mermaid, cuz my bikini matched my tail!

[Trade Winds]

I went up a size though. I fit into their Women's Small tail size, but got a Meduim bottom.

I gave up and just did this lol. Easiest thing to do, altho I like the scarf/belt idea and will give it a try!

[Spindrift]

I second the tights idea, or even bike shorts.