I love going to the beach, and I wish I could combine my love for the sea with excercise. What type of movements can I do in the sea so it'd be more like a workout rather than just chilling in water?
Sorry if this sounds weird, but why not actually go swimming?
Assuming you know how to swim and it is safe there (life guards, weather conditions, cordoned off, etc) then swimming is an amazing workout. It's even more of a workout with some waves and it could cover multiple muscle groups plus improve endurance and breathing. Low impact on the body as well.
The most simple exercise would be breast stroke as you can be relatively stable and have good visibility of what's in front of you. You can make it harder by doing it under water as long as possible to increase resistance and improve endurance and breathing.
If you don't want to go out deep into the sea how about treading water. This will also give you a work out as you work on staying afloat while coordinating legs and arms. To make it more difficult, keep your arms up like you're trying to keep something dry/put hands on your head so you only use the legs. Add on treading while moving to one side of the beach to the other.
You can jog about 100 yards and back in the low, wet sand to warm up with less resistance and do some but kicks and high knees during the run, also take some time to stretch your calves, hamstrings, quads and glutes. If you are not used to running in the sand it can easy to pull a muscles.And swimming is obiviously one of the exercise.And you can also do spiderman crawls and push ups and also shoulder ups
and you can also do some frog jumps this is not easy to don in sand but this is very helpful because these beach workout challenge your entire body.Working out on beach test your stability,fitness level and mental toughness due to unstable surface.I hope this enough.