I think it's more or less the same in Bossa-mode, but pushing forward/backward still pitches your fish nose down/up, so avoid pushing forward/backward. Then keep "swimming" to flop along. And I think you need to aim to move sidewards. I think it rolls to its right. So, for example, if you have its nose at the left of the screen, you'll be moving forwards. Quite hard in Bossa-mode, as it's meant to be - infuriatingly so at times - but doable with practice.

NOT WHEN IN THE JAR

I seem to be able to control the flailing when in the normal control mode but in Bossa-mode I have no clue what I need to do to move the right way.
Doesn't help that I can barely control my jumps in that mode so end up landing short of where I want to be 90% of the time

Sorry for any bad grammar or spelling

Here is how to move on land:
I recommend a game pad or controller. Look in the direction you want to go (presumably the water, obviously), and your stick forwards. The fish will proceed to flail, jump, and roll in that general direction. trust me, I've played for 23 hours (which is a little embarrassing)
*** Pro tip: If your bowl breaks when you are "That" close to the checkpoint, use this method to move towards the checkpoint. The game will recognize the fish and let you collect the checkpoint, re-spawning you there when you die. ***
I hope that helped. (Honestly I haven't played in a a year or 2 so they may have patched this)

YOU

Same issue/ On land no control at all. Just jerks and dies. No logics, can't understand how to make it move in the needed direction.

people help me , the game does not INSTALL , please help me