My thoughts are thus, usually at a Beach Scene, applying lotion in very lewdly suggestive areas or the shower scenes to wash off the sand are givens in most VN's featuring beaches; however we don't see other issues that could  arise when exposed to the searing heat for long periods of time, things that would effect the characters negatively yet ultimate being character closer together. for example;

1. Heat Exhaustion or Heat Stroke, causing dizziness, nausea/vomiting (granted this doesn't have to be seen obviously) high body temperature, this could be brought on by excess consumption of alcohol, see where I'm heading with this one? (more on this later)

2. Sun Burns, the mild one being home treated with cool baths/showers or more serious cases leading to flaky and dry skin, therefore needing moisturiser to be applied.

3. Dehydration, this one should be self explanatory, when being dehydrated you need 'fluids'; Water, Milk, 'Juice', you get the picture.

In just these three alone, many scene and scenarios could present itself; 2 and 3 being the more obvious scenes playable, however 1 could have an entire Chapter to the story if needs be here's a brief;

Chapter starts, everyone preparing for the trip to the beach, local or distant, could also play a factor here, being local character could walk to it, enjoy pleasant conversation, while also still being exposed to the sun and thus begins our 'problem'. If set for a distant beach, this could draw out more time as MC perhaps wants to help others pack if there were to stay in a hotel for a day or so (already this opens up more expansion to the chapter so as to be able to spread this over several days).

In both branches at this point you could perhaps throw in a blown tyre forcing the MC to help change it being the 'man of the house' and all (again this could play to the more hostile character to either tease or taunt the MC). During this pause while the MC is working up a sweat, becoming dehydrated, a lack of provisions for the trip could play a factor here too.

(Distant Beach Route) perhaps a Mix up in the hotel booking forces them all to share a room seeing as so many wish to take full advantage of the heat (this could also be a reason why Catherine turns up later than the others to the beach)

Finally at the Beach, maybe they are in luck  and there's a beach bar or even a party and Alcohol is flowing-a-plenty.

Now here is where we get to the Meat and Potatoes, consumption of Excess Alcohol can cause many of the same conditions are heat exhaustion, Dizziness, Nausea/Vomiting. (hopefully you see my vision here)

Showing clear signs of being intoxicated, 'victim' (be it MC or another Character) is teased and made fun of, they go to bed out of 'exhaustion' only to be unable to wake the following morning with fever and high temperature, thus the reality of the situation hits home and commence 'treatment' and recovery where those feeling guilty for not recognising the true symptoms of Heat Exhaustion or Heat Stroke, dependant on how far you wished to take the situation, and therefore bond over jokes or teasing of the situation.

Well this of course is just a scenario I had in my head and the more I thought about it and how it'd play out the more I've typed, only realising just now how much I've actually written -_- Anyway, I do hope this gives you some Ideas on what scenes you could use. Looking forward to seeing what you come up with though.

Regards

Racer

I got confused but in case it counts if I comment here... I would love more catherine scenes especially in a swimsuit if it is even an option... but other than that a sneaky hidden sex scene would be ok with me it kinda basic but sneaking one at the beach would be nice btw will we see catherine in a swimsuit on the beach? I know this post is for these 4 girls but im curious? But if I had to pick one out these 4 Samantha deserves more she has just 1 threesome scene and I would like that sneaky hidden sex to be with her. Just a suggestion if it even counts here.