Dipping into a kosher Mikveh [i.e. Ocean]: [1]
One who is traveling on the road and does not have a vessel with which to pour the water onto his hands, then he should dip his hands into [a Kosher Mikveh, such as] a puddle of 40 seah worth of rainwater, or a wellspring, even if it contains less than 40 seah, and then say the blessing of Al Netilas Yadayim.[2] [However] if later on one accesses a vessel, then he should pour from the vessel three times [inconsecutively] onto his hands.[3]
[1] Siddur; 159:21-22; Seder Netilas Yadayim 8 regarding washing for bread; Nehar Shalom 4:2 in name of Rashba; Chayeh Adam 7:4; M”B 4:25; Shulchan Hatahor 4:8
[2] The reason a blessing is said: Some explain a blessing is said being that impurity is removed from the hands when one dips it three times in a Mikvah of 40 Seah. [Olas Tamid 4:6; M”B 4:25] Others however rule that based on the Zohar it is questionable whether the impurity is removed through dipping. [Elya Raba 4:7; Machatzis Hashekel on M”A 4:10] Nevertheless even according to them a blessing may be said as the reason behind the morning washing is not only to remove the impurity but also to prepare oneself like a Kohen. [Kaf Hachaim 4:45 based on Michaber 4:22; Admur Kama 4:3] However based on Admur in Basra that the reason behind the morning washing is due to the removal of impurity then one must say that some impurity is removed through dipping, as rules the Olas Tamid. Furthermore in the Siddur it is implied regarding the ruling in a case that one does not have enough water to wash three times that we only allow a blessing to be said because even one pouring removes some part of the impurity, and thus sanctifies a person. [See Halacha 12] Thus, here too if the dipping does not remove any of the impurity, how can we allow a blessing to be made? Hence, perhaps according to the Siddur dipping in a Mikvah removes some of the impurity. Vetzaruch Iyun.
The Nussach of the blessing: In 159:24 and Seder Netilas Yadayim 9 Admur rules that it is best to say the blessing of “Al Shetifas Yadayim” when dipping the hands in a Mikvah. Here however he rules one is to say Al Netilas Yadayim. Vetzaruch Iyun. To note that the Ketzos Hashulchan 2:8 writes one is to say “Al Netilas Yadayim”.
[3] Siddur ibid; Seemingly the reason for this is because it is possible that the impurity only becomes removed from the hands through pouring from a vessel. [Beir Heiytiv 4:12; Kama 4:12] However, based on the Siddur [see previous footnotes] one must say that dipping in a Mikvah removes some of the impurity. Hence washing three times is only needed in order to fully remove it. Vetzaruch Iyun.