Wifi connectivity is inconsistent

Device situation:

• The phone has a thin rubber case.
• It has had a few falls at around or less than 1m (3ft).
• The screen and rest of the phone are fine, no cracks, very few dents
• It went for a 3 second swim in the toilet (luckily just after cleaning and before using), I turned it off and placed it for 2 days in a bag of rice, which seems to have fixed it.

The problems:

The phone has 3 major issues, the wifi connectivity being the focus in this post, however to be thorough I want to mention all here:

• camera partially blurry
• power button not working
• very poor connectivity on wifi (have to constantly put plane mode on/off to get internet back)

Further description:

I use my phone a lot. Always connected to internet either by 3G (my country's LTE band is 28 on all providers, and this iPhone does not support it), or by Wifi.

When on 3G, the internet is slow (of course0 but it is there. However sometimes, when I'm on wifi navigating, I would get a "no internet connection", while wifi signal (as per the logo on the top of the screen) is nice and strong.

In order to get internet again, I have to switch plane mode on, then off again.

Questions:

I'm wondering if this is actually a problem with my phone or an issue with my router/DHCP?

If there was some physical damage from the swim or otherwise, I probably would not be able to connect at all, would I?

I still ask the question here since I have 2 other problems with the phone that could be correlated (just assuming here, I've no real idea)

Thanks

Questions regarding the other issues mentioned here:

• Rear camera photos are partially blurry
• Power button not working