This is my friend's phone, that's why I don't know the OS Version. (she doesnt allow access to her settings )

I was playing with my friends on a WLAN world on a tethered WiFi Hotspot on the same phone running the world and then I suddenly disconnected, afterwards, I logged in and I spawned in an ocean, where the floor was flat and made of gravel, no sign of land even wherever I swim and the only way out was to drown myself. Luckily, I placed all my items in my chest before I disconnect, otherwise I should have lost my items. When I killed myself, I was able to go back to the spawnpoint

Before the drowning, we tried to:

• Relog
• Change Username
• Swim about 50 blocks away from teleported area