I'd never recommend taking hit from debris, especially with rocks likely as big from the stone dragon. Way to iffy. Also that dome covers mainly you in the frontal region, what about the rocks that might bypass it from the sides? What about the whole water as a whole? I can just continue and cause you to lose balance from the amount of water spewed, especially knowing how much water I can make and how small that dome is, once again its iffy. I wouldn't say you would get hurt but it leaves you in a vulnerable position. I'm sure you have heard of Bruce Lee's famous water quote, check that out for an idea.
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Lancer noticing the the rather small dome, stopping the water in front of the opponent but still flowing along the terrain, Lancer simply performs one hand seal and creates a center hole right behind you're position, forcing it to spiral inward sucking everything in mid-long range but just out of Lancer's positions reach. What this causes is not only you to be dragged in, but with the water all over the area it will also suck the water inward carrying you and immobilizing you even further with the high volume of water, the speed of the antlion and the overall position where it is created, physical movements (basic) is almost impossible and you will be dragged in suffocating from the water and getting buried alive.
(Doton: Arijigoku no Jutsu) - Earth Release: Antlion Technique
Rank: B
Type: Offense
Range: Mid/Long
Chakra Cost: 20
Damage Points: 40
Description: The user performs the Ram hand seal and causes causes the ground and everything on and around it to be sucked in towards the middle of a large pit, much like the method an antlion uses to catch prey. Upon being dragged to the centre, the victim will then be sucked underground. There the victim, depending on how deep the user makes them sink, will be trapped and/or suffocated. The range of the pit is determined by how much chakra is put into the technique.