EF3/4 Sentence combning "Seawall"

Nice mix of sentence styles:
simple
compound
complex

1. We were riding bicycles on the Seawall. Simple
We were riding bicycles, and we rode on the Seawall. Too much- overwritten
When we were riding bicycles, it was on the Seawall. Complex

2. Our bicycles were rented, red and white. AWKWARD
Our bicycles were rented, and red and white. SIMPLE
Our bicycles which rented were red and white. 
COMPLEX
Our bicycles which were rented were red and white. 
Our bicycles which we rented were red and white.
Our bicycles which were red and white were rented.
Our rented bicycles were red and white.
SIMPLE
May I rent a bicycle which is red and white? SIMPLE

I rented a bicycle. Active voice
The bicycle was rented. Passive voice

3. We wore helmets which were required.
We were required to wear helmets. Natural sounding

You are required to wear a seatbelt when you drive a car.

5. The ugly helmets were for safety.
The ugly-coloured helmets were for safety. SIMP
The helmets were an ugly colour which were for safety. XXX
The helmets which were for safety were an ugly colour. CMPLX
The helmets which were for safety had an ugly colour.
We wore the helmets for safety even though they were an ugly colour. COMPLEX - ADV CL

6. The Seawall was busy and crowded.
The Seawall was busy and also was crowded.
The crowded Seawall was busy.
The Seawall was busy because it was crowded.

Because the Seawall was crowded, it was busy.

The Seawall was crowded, so it was busy.

When the Seawall was crowded, it was busy.

The Seawall was crowded; therefore, it was busy.

The Seawall that was crowded was busy.

The Seawall, which was crowded, was busy.

SIMPLE

COMPOUND

COMPLEX

That is all you need for any level of writing.

Skeletons of the sentences - the bones

The foundation

7. People were walking and rollerblading.
Some people were walking, and others were rollerblading.

8. We rode slowly, and I rode in the middle.
We rode slowly with me in the middle.

They rode slowly with me in the middle.

When I was in the middle, we rode slowly.

We rode slowly because I was in the middle.

9. My brother rode in front while his friend rode behind.  COMPLEX

When/While my brother rode in front, his friend rode behind.
My brother rode in front, and our friend rode behind. COMPOUND
My brother rode in front and our friend behind. SIMPLE

10. After we rode for an hour without stopping, I was out of breath and my legs were sore.
I was out of breath because we rode for an hour without stopping, and my legs were sore. COMPOUND COMPLEX
We rode for an hour without stopping; as a result, I was out of breath and my legs were sore. COMPOUND