```ts
export function tideMarks(levels: number[]): number[] {
  if (levels.length < 3) return [];

  const peaks: number[] = [];
  for (let i = 1; i < levels.length - 1; i++) {
    if (levels[i] > levels[i - 1] && levels[i] > levels[i + 1]) {
      peaks.push(i);
    }
  }

  return peaks;
}
```