This scenario is fairly easy and should be a good introduction to Soaked!.
To start any and every scenario, you should immediately pause the game. While the game is paused, check the staff, the status of the rides, the cleanliness of the park, financial status, the objectives and the landscape. Everything is in good order, and there are no pressing issues that need to be fixed. Note that the objectives of this scenario are number of guests in park, number of guests in a clean pool complex and park rating.
Both the guest and park rating values are fairly easy to reach, and will come with a good pool system, so your first priority should be to build a pool complex. A good place for this is the inland flat area to the right of the Spin Doctor, viewing from the sea. Make sure that the pool has loungers, hot tubs, diving boards and ladders, as peeps will bore easily of a basic pool. You will probably want to build a waterslide, maybe even multiple water slides, as it is difficult (but not impossible) to attract the peeps needed to the pool without them. Keep the price low, no more than $1.50, to keep attracting peeps to the pool. Assign a janitor and mechanic to the paths around the pool complex. Check the thoughts of the peeps in the pool complex. If you are getting "This pool is great!" and "<pool complex name> is a really good value", then you can move on to the next goal; just make sure that the level of the peeps in the pool continues to increase. If you find that the number is not rising, build a waterslide or two and lower the price by $0.20, and continue to improve the pool as needed until you eclipse the 150 guest mark.
The next priority should be to build concession stands. An advisable strategy to build a food and a drink stand by the entrance, and a larger food court near the pool complex. Make sure there are adequate benches and trashcans near the food stands, along with janitors and mechanics.
Once your pool is built and the food situation is addressed, just place flat rides, and perhaps a roller coaster, on the beach and nearby the pool complex. Delete the Disko and Spin Doctor if you like, but don't delete the Sky Rider. It is a popular coaster and does a good job attracting peeps. Just following this simple strategy, you will reach the objectives easily.
The pool- designing skills that you will learn from this scenario will prepare you for the more challenging Soaked! scenarios approaching.