Spring is definitely a good option for making a naval themed war game. However, if the game is part of an assessed project you should check your requirements. The work required for Spring will probably put you beyond the intended scope of the project. I assume you are doing some sort of programming/computer science/AI course because you have been told to implement crowd simulation (as opposed to a game development course where I imagine they would tell you to make a game). If this is the case then Spring will require you to do a lot of 'irrelevant' things such as find/creating 3D models, animation, effects, possibly map design etc... For a basic game you don't need to put too much work into these aspects but the sheer number of them will add up and give you a lot to learn.
Making a game with Spring will not give you experience implementing basic RTS functionality. Spring has pathfinding, terrain, resource management, unit selection, a command queue handling system, some physics, a weapons/aiming/damage system. Most things which are common to every RTS are in Spring (in some form). Game development definitely requires programming but it will mostly be for uncommon game mechanics, UI layout and animations.
You might want to check out Love:
https://love2d.org/ . It is a 2D engine which only handles basics such as including graphics and sound. The art requirements are significantly smaller for 2D and you will have to implement basic RTS functionality such as unit selection and pathfinding. This might make your assessor happier.