Whale Skip

In Dive Man's stage, you can skip the 2 whales using Balloons:

For RTA purposes, this only could save time on the second Whale as you'd need to menu here anyways. This can be useful if you have issues mashing this Whale. 

Disadvantages

You most likely will need to wait to touch the ground again to go, note that you can make it past the Wire pit although you have to be really confident and a very good position, chaining this is quite inconsistent, if you see mega man during the transition you will have to abort otherwise you will fall into the pit.

While it saves time on the Whale screen, since you are in the air for quite long, the next room will always be slower than the regular way of doing it.