The ticker says it all, these guys are drillers, ocean drillers to be more precise. Deep water drilling is expensive and in order to survive the price of a barrel of oil extracted under these circumstances is somewhere in the order of >$110. No wonder then that demand for their services has dropped off a cliff.
These are both semi-log charts. When the movements are very large, as they are here from $195 to $15, the semi–log scale gives a better expression of the proportions of the movement within the frame of the chart. Looking at the Bigchart we suspect that we have an a-b-c, with the b being a triangle. We are not sure where the a ends and the triangle starts (it could be one step to the right from what is shown in red ), but this does not change the essence of this corrective structure.
Often the c is (vector) equal to the a. That suggest a low of about $12. If that is all there is to it, this stock would be a buy right now. However, c waves always subdivide into 5 separate waves and , so far at least, we appear to be missing a good part of 4 and all of 5. So this correction is not yet finished. It may take a while, maybe a year.
If you believe oil will shoot back up soon (I do not share that opinion), than Transocean must be one of the better buys given its leverage to oil.